This dish is excellent for lunch or as an appetizer when tomatoes are in season. This recipe requires a 9-in (20-cm) tarte pan which, in contrast to a pie pan, has a removable bottom and straight sides. Recipe from New World Provence: Modern French Cooking for Friends and Family, published by Arsenal Pulp Press.
In a food processor, add flour, salt, and butter, and pulse until butter resembles small peas. Add egg yolk and continue to pulse to combine. Add ice cold water and pulse again until pastry separates from sides of bowl (may need extra ice cold water if this isn’t happening).
Remove dough and knead on a lightly floured surface for 1 minute. Form into a ball, cover with plastic wrap, and refrigerate for 1 hour.
Remove dough from refrigerator and roll to fit a 9-in (20-cm) tarte pan. Brush mustard over dough.
Distribute cheese evenly over mustard. Arrange tomatoes on top of cheese and top with onions and olives. Bake for 30-35 minutes, until crust is golden brown. Serve warm, drizzled with oil and sprinkled with salt and pepper.