This takes an hour an a half to make, but most of it is cooking times. So easy to make.
You will need:
- one package frozen puff pastry
- 6-8 roma tomatoes (depending on size)
- 2 yellow onions
- teaspoon dried basil
- pinch of sugar
- olive oil
- 1 cup imported gruyere, shredded (don't buy domestic gruyere, it tastes disgusting)
- 1/4 cup half and half
Turn oven to 300. F. Slice tomatoes, crosswise, 6 slices per tomato. Spread out on parchment covered cookie sheet. Place in oven. Set timer for 45 minutes to start. Do not skip this step! A soggy tart is one too many. Roasting the tomatoes takes some of their moisture out and makes them smokier.
Halve and thinly slice onions. Warm oil over low heat. Add onions and stir, occasionally for 20 minutes. Keep the heat on the low side. You are not frying the onions, you are sweating them.
After 20 minutes or so, when they seem nice and soft, add your basil and pinch of sugar. Continue to cook for another 20-30 minutes, until they are just starting to turn golden. If you keep the heat at medium low you only need to stir every 5-10 minutes.
Check the tomatoes. You can turn them over if you wish, but I didn't bother. Once they are looking nicely roasted, take out of oven and turn oven to 450.F.
Assemble the tart:
Your puff pastry should be thawed. On the largest baking sheet you have, put the sheets side by side and overlap by 1/4 inch. Press the seam with your fingers. Press up edges of tart to make a little rim. Space tomatoes on tart and spread out onions on top.
Bake for 15 minutes.
Meanwhile, mix gruyere and half and half.
After 15 minutes, take the tart out and spread the cheese mix over the tart. Slip back into oven for 6-7 minutes, until just the top is starting to turn golden.