I am a bruschetta pedant. So please, bear with me as I whine for just a minute about a couple of the biggest sins committed against Italy's most famous tomato-topped toast.
To start, it's pronounced brew-SKET-ta, not brew-SHET-ta. I admit that mispronouncing a name isn't a true transgression, but in this case, it's enough of a pet peeve of mine that I couldn't resist the opportunity to correct literally thousands upon thousands of people all at once. Sometimes it feels good to be a jerk.
Also, bruschetta is not synonymous with "tomato bruschetta." Tomato happens to be the most common topping in the United States—to the point of being the expected topping—but, at its simplest, bruschetta is nothing more than toasted bread brushed with olive oil and rubbed with garlic. From there, it can go in any number of directions, topping-wise.
With that done, now I'll tell you the third, and much more significant, assault on tomato bruschetta: using crappy fresh tomatoes. Just like with a Caprese salad, there's only one acceptable time for making fresh tomato bruschetta, and that's when tomatoes are at their seasonal peak. Making bruschetta with out-of-season tomatoes is never a good idea, no matter how appealing it may seem. You may as well attempt to make barbecue out of a pack of Slim Jims.
Am I being dogmatic about this? Yes. But I also have a solution for those occasions when you want tomato bruschetta in the off season. Below, I'll explain both ways to do it, using fresh tomatoes for those few weeks or months when they're truly ripe and flavorful, and using canned tomatoes and an oven for the rest of the year.
Fresh Tomato Bruschetta
Bruschetta is one of those foods that are so fundamentally simple that there's no hope of hiding mediocre ingredients behind technique or presentation. If your tomatoes aren't great, your bruschetta won't be either.
Most versions are made by tossing fresh diced tomatoes with basil, garlic, and olive oil; spooning it all on toasts; and drizzling it with balsamic vinegar. I do it more or less the same way, though there are a couple of key points where I sometimes differ.
At the risk of belaboring the point, let's talk about the tomatoes just a little bit more. I've already said that they need to be ripe, but just how ripe is that? They should be heavy for their size, and when you gently press on their skins, they should feel exceedingly fragile, like taut water balloons on the precipice of bursting. In short, if you toss a bunch of them in a bag, then jostle and bump them around, and not a single one bursts open or splits, they're probably not ripe enough.
I like to use a mix of heirloom varieties, which offer not only a confetti-like rainbow of colors but also a blend of flavors; some sweeter, some more tart. Some can be fleshier paste tomatoes, like plums, while others can be juicy with seeds. I even like to toss in a couple of handfuls of sliced cherry tomatoes, to get other shapes aside from cubes.
A lot of recipes say to seed the tomatoes so that you're left with only the drier diced flesh, but I'm against this, since the seeds contain so much great flavor. For the same reason, I don't like to pre-salt my tomatoes and drain the juices, as other recipes suggest.
Instead, I prefer to embrace the fruit's natural juiciness—all that tomato water can soak into the toasts, adding even more flavor. I put the salt on the toasts and tomatoes only at the very end, like a garnish. (A nice sea salt or flaky finishing salt is great for this.)
I also prefer not to mix minced garlic into the tomatoes, since the bits of raw garlic can sometimes taste too harsh. I find I get better control over the level of garlic flavor by making what the Italians call fettunta, in which you rub raw cloves into the toasts themselves before drizzling them with olive oil. The cloves dissolve as you rub the toast with them, and you can add as much or as little as you like, while ensuring that each bite of the toast and tomatoes has an equal amount.
It should go without saying that you must also use the best olive oil you can, so I'll move on to a less obvious issue, regarding the vinegar. Bruschetta is most often made using balsamic vinegar on the tomatoes. I'm not opposed to this per se, but I caution against it unless you have the truly good stuff. Real balsamic is a very expensive condiment, naturally syrupy, with a complex sweet-tart flavor. If you have it, go ahead and drizzle it on the toasts.
The problem is that most of the balsamic out there is not the real thing, but an ersatz concoction made from some cheaper vinegar pumped up with caramel color and flavors. It's also nearly as thin as water, which makes it impossible to drizzle on top of your toasts. If this is the type of balsamic you have, then I'd encourage you to not bother with it here, as it will add very, very little. Instead, taste your tomatoes, and if you think they need a little hit of acidity to balance their flavor, just add a splash of red or white wine vinegar; it'll deliver just what's needed without getting in the way.
Oven-Roasted Canned-Tomato Bruschetta
Whenever tomatoes are out of season, you should walk right past the produce section and head straight to the canned-foods aisle to grab a couple of tins of peeled whole tomatoes. Unlike out-of-season fresh tomatoes, canned tomatoes really are picked when ripe and then processed right away, which means they'll have significantly more flavor. But one result of the canning process is that those tomatoes are cooked, leaving them soft and mushy, and therefore nearly impossible to dice. Since there's no way to reverse the clock and return them to their uncooked state, the best thing to do is to embrace it by slowly cooking them even more in a low oven. You'll end up with concentrated, jammy-sweet tomatoes that make a killer bruschetta-style topping for toasts. (It's a method we used back when I worked at the chef Cesare Casella's Tuscan restaurant Beppe, in New York City.)
Because cooked tomatoes have so much more free liquid than fresh tomatoes, driving off excess moisture is key to this process. So, in this case, I start by draining the canned tomatoes and tearing each one open to discard its wet seeds.* I then arrange them on a parchment-lined rimmed baking sheet, drizzle with olive oil, season with salt, and transfer them to a 300°F oven to cook, until their excess juices have completely evaporated and the tomatoes have taken on a deep red color. This should take roughly one hour, though that time will vary depending on the oven.
* In canned tomatoes, those seeds have also already given up much of their flavor to the rest of the flesh, which means that we don't take a huge hit on flavor by discarding them.
I chop the oven-roasted tomatoes, then mix them with fresh basil, olive oil, and wine vinegar. It's difficult to give an exact quantity for the vinegar, because this will depend heavily on the flavor of the specific canned tomatoes you're using.
It's best to add a splash, mix it in, and then taste it before deciding whether to add more or not. A pinch of sugar can also sometimes help nail the perfect balance of sweet-tart flavor you're going for, but go easy on it.
I spoon this oven-roasted bruschetta topping onto slices of fettunta (garlic and olive oil toasts), just as I do with the fresh-tomato version.
Some folks may say this isn't true bruschetta because it's not made with fresh tomatoes, but I'm pretty sure just one bite will convince them that it's worlds better than the out-of-season alternative. Then we can all be bruschetta pedants together, and our food will taste better for it.