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For the crust:
one sheet puff pastry, defrosted in the fridge overnight, or at room temperature for 45 minutes.

For the marinated tomatoes:
1/2 teaspoon sugar (optional)
2 medium size garlic cloves
½ cup coarsely chopped fresh basil leaves, lightly packed
1/4 cup whole fresh parsley leaves, lightly packed
1/2 teaspoon Kosher salt
¼ teaspoon freshly ground black pepper
¼ cup extra virgin olive oil
1 1/2 pounds firm small size tomatoes about 2 ½-3 inches round, cored and sliced 1/4 inch thick —about 4-5 tomatoes

For the tart:
2 Tablespoons Dijon mustard
1 Tablespoon full fat sour cream
2 oz. freshly grated Parmesan cheese, 1/4 cup plus 2 tablespoons, divided
one large egg beaten with one Tablespoon heavy cream or milk
4 oz. grated Gruyere cheese, about 1 cup

Make the tart:
       Preheat the oven to 400 degrees F, and line a sheet pan with parchment paper.
       In a medium size bowl, add the sliced tomatoes and sprinkle with the sugar. In a food processor fitted with the steel blade running, drop the garlic cloves through the feed tube to mince them. In the same bowl of the food processor add the parsley, basil, garlic, salt, and pepper. Process until the herbs are finely minced. With the processor running, pour the olive oil down the feed tube and process until combined. Pour the mixture over the tomatoes and toss gently. Set aside.
       In a small bowl, combine the mustard and sour cream. Set aside.
       In another small bowl, make the egg wash by beating the egg and heavy cream together with a fork or small whisk until smooth.
       On a lightly floured piece of parchment, gently unfold and roll out the puff pastry into about an 11 x 13-inch rectangle. Slide the piece of parchment onto a sheet pan. Prick the dough all over with a fork and bake in the center of the oven for 10-12 minutes until puffed.
       Remove to a heatproof board or on top of the stove. Be careful working with the dough on the hot pan.
       Leaving a one inch border, drop small dollops of the mustard mixture evenly all over the hot dough and use a spoon or off-set spatula to evenly coat. Sprinkle the ¼ cup of the Parmesan over the mustard layer. Liberally brush the 1 inch border with the egg wash. Overlap the tomatoes, draining them as you go, in 3 rows lengthwise. You’ll need about 5 slices for each row.
       There will be some of the garlic and herb mixture leftover. Strain some of it, you can just do that with your hand, and distribute some of it evenly over the tomatoes. Any extra can be used as a delicious salad dressing with some added vinegar. Evenly sprinkle the Gruyere and the remaining 2 tablespoons of Parmesan on top, making sure to sprinkle some on the egg-washed border as well. Bake for another 25-30 minutes, rotating once front to back, until the edges are a deep burnished brown and the cheeses are melted and lightly browned.
       Cool slightly, cut into 9 squares, and serve warm or at room temperature.

Makes 3 servings.(and easily doubled)      YUM!

LESSONS Learned:
1. Although a quick alternative to pie crust, be careful not to let the puff pastry get too warm. The butter between the layers might melt and it won't puff. My favorite brand is made by Dufour, but Pepperidge Farm works well too.
2. To easily slice the tomatoes, use a serrated knife.
3. to make the tart pretty, I like to use evenly sized slices, so I don’t use the end slices of the tomatoes for this tart. I usually get 3-4 slices from the center of each tomato. I put the chopped ends in the leftover marinade to add to salad.
4. You can switch out the cheese, herbs and spices. One option might be Monterey jack with minced jalepenos, garlic, parsley and some cumin, or how about mozzarella/parm, prosciutto, fresh basil and oregano.