Prepare dough by pulsing flour, 1 egg, 1 egg yolk and salt in a food processor. Add butter, piece by piece, pulsing until all is incorporated. Add water and pulse only until dough forms a ball. Remove; cover with plastic wrap and refrigerate at least 2 hours. Remove dough from refrigerator 30 minutes before assembling tarts.
Meanwhile, prepare filling by cooking onions in butter in 2 large skillets until tender and translucent. Cool in a medium bowl. Beat 4 eggs, 2 egg yolks and cream together. Stir into onions; add cheese, bacon, chives and salt and pepper to taste.
Preheat oven to 350 degrees F. Divide dough in half. Roll each portion to fit in 10-inch tart pan with removable rim. Trim dough to fit rim height and prick bottom of dough with fork. Bake crust 7 minutes or just until it begins to turn golden brown. Remove from oven, add filling and bake 15 to 20 minutes more until egg mixture is set. Let cool 5 minutes before removing rim from tart pans. Cut into wedges.
Note: The chef serves this tart with salad of baby spinach, red and yellow teardrop tomatoes, sliced Hass avocado, toasted pecans and apple cider vinaigrette.
Recipe by Chefs Frank Randazzo and Andrea Curto-Randazzo