Preheat oven to 425 degrees. Arrange racks so one is in the middle and one is in the upper third.

Thaw puff pastry for 20 minutes. Open it up to allow air flow for faster thawing.

Flour a work surface and roll puff pastry out to the size of a cookie sheet.

Transfer pastry to a parchment-lined cookie sheet.

Poke holes all over the pastry to prevent it from puffing up too much.

Place another sheet of parchment over the pastry, then place another sheet pan on top. This prevents puffing and ensures even thickness.

Bake on middle rack for 25 minutes until lightly browned.

Remove from oven and cool on a wire rack.

Wash tomatoes and cut them in half crosswise.

Place tomatoes in a bowl and toss with olive oil, thyme, salt and pepper.

Arrange tomatoes on a sheet pan cut-side up and bake on upper rack for 15 minutes.

Remove from oven and let cool.

Whip ricotta cheese with a mixer until light and fluffy. Alternatively use a food processor.

Spread whipped ricotta over cooled pastry and season with salt and pepper.

Arrange roasted tomatoes on the cheese cut-side up, keeping them in nice rows and columns for easy cutting.

Using a sharp knife, slice pastry into squares, making sure each tartlet has one tomato.

Taste one and adjust seasoning as needed with additional salt.