Tomato Tarts

Why I Love This Recipe
I really didn't know what category to put this in because I have used these for a brunch or luncheon main dish, as a side, for entertaining and for vegetarian. I first tasted these at a place called Olga's Cup and Saucer in Providence, RI and I asked for the recipe. They scribbled down how they make it, but couldn't scale it down, so I did my best and I think this one's the winner. I use all my heirloom tomatoes at this time of year.
Ingredients You'll Need
1/2 pound butter
2 cups flour
1 teaspoon salt
1 tablespoon sugar
1/4 cup ice water, or as needed
1 medium onion, sliced
1 tablespoon olive oil
butter, softened, for brushing pie tins
cornmeal, for sprinkling on pie tins
8 medium tomatoes (I use heirlooms)
2 tablespoons dijon mustard, plus 2 teaspoons
1 cup shredded cheddar cheese
salt and pepper, to taste
2 tablespoons olive oil, plus 2 teaspoons
1 large egg white
8 fresh basil leaves
8 small aluminum pie tins
Directions
Make tart dough:
Put in the food processor the flour, butter, 1 tsp. salt, and sugar.
Pulse quickly until the butter is the size of peas.
Add the water in a small stream until the dough just comes together.
Empty dough from work bowl and form into 2 balls.
Wrap in plastic and chill till ready to use.
Make caramelized onions:
In a skillet heat the olive oil and cook the onions till golden.
Remove from heat and let cool a bit.
To assemble tarts:
Take the pie tins and brush all inside with softened butter.
Sprinkle with cornmeal.
Cut dough into 8 equal pieces and put 7 back in fridge. On a floured board, roll out dough into a 6 inch circle.
Place dough in pie tin and repeat till all 8 are done.
Preheat oven to 375 degrees.
Brush bottom of dough shell with 1 tsp. of dijon.
In the following order place into each shell: 1 Tbsp. cheddar cheese, 1 Tbsp. onion, 4 thick slices of tomato, salt and pepper, 1 tsp. olive oil drizzled, and a basil leaf.
Fold in the overhanging flaps of dough around the tomatoes, crimping if needed.
Brush dough with egg white.
Bake for 30-45 min. or till nicely browned.
Let sit for an hour before serving.
The tarts will look very rustic.