Heirloom Tomato Tart

Why This Heirloom Tomato Tart Works

In the oven, the cheese under the tomatoes starts to melt and soften first. That bottom layer soaks up some of the tomato juice, so the crust is protected and stays more crisp instead of turning soggy. As the heat keeps going, the tomatoes give off more juice, but they also start to dry a little on the edges and become more tender and sweet.

Up top, the mayonnaise mixed with mozzarella, Parmesan, basil, and garlic slowly melts and thickens. It goes from a loose spread to a soft, cheesy layer that settles down around the tomato slices. That cheesy topping traps some of the moisture from the tomatoes and holds everything in place, so the tart slices cleanly instead of falling apart.

By the time the crust is golden, the cheeses have bubbled and set into a firm but creamy layer. After it comes out of the oven and sits for a few minutes, the hot juices calm down and thicken a bit, so the tart holds together when cut.

Mistakes To Avoid

Slicing the tomatoes very thick or not draining off extra juice leads to a soggy tart. The tomato slices release a lot of liquid in the oven, and if there is too much, it soaks into the crust. The bottom then bakes up pale and wet instead of firm and crisp.

Skipping the cheese layer under the tomatoes causes the same soggy problem. That first layer of mozzarella and Parmesan acts like a barrier, catching some of the moisture as it melts. Without it, the tomato juices go straight into the crust and keep it from setting.

Baking at a lower temperature or pulling the tart out too early leaves the center loose and the crust underdone. The cheese topping may look melted, but the bottom can still be soft and doughy. Slices then collapse and the tart is hard to serve cleanly.

Cutting into the tart right away instead of letting it cool a bit makes the filling slide out. The hot cheese and mayo mixture needs a few minutes to firm up. When it is sliced too soon, the topping runs and the pieces lose their shape.