Cheese Filled Torta

Dough may be started one day ahead
Dough:
2 envelopes dry yeast
1 C warm water (105-115)
1/2C (1 stick) butter, melted
3 eggs
1T sugar
1 tsp salt
4C unbleached all-purpose flour

Filling:
2T olive oil
2 small onions, thinly sliced
1/2C minced red bell pepper
1/2Cminced green bell pepper
1/2C freshly grated parmesan cheese
1/2 tsp coursely ground pepper or dried red pepper flakes (optional)
1 pound shredded Fontina or Monteray Jack cheese (about 4C)
1 egg beaten with 1T milk (for glaze)

For dough:
Sprinkle yeast over warm water in large bowl; stir to dissolve. Let sit 5 minutes. Whisk in butter, eggs, sugar and salt. Add flour 1 cup at a time and mix until smooth dough forms. Cover and refrigerate at least 2 hours. (can be done 1 day ahead)

For filling:
Heat oil in heavy large skillet over low heat. Add onions and bell peppers and cook until onions are translucent, stirring occasionally about 15 minutes. Cool completely.

Grease 12" round pizza pan. Divide dough in half. Roll 1 piece out on floured surface to 12" round. Transfer to pan. Press edges to form 1/2" high rim. Sprinkle dough with parmesan cheese, then top with onion mixture. Sprinkle w/pepper if desired. Cover with Fontina or Monteray Jack.

Roll remaining dough out on floured surface to 12" round. Cut into strips 1" wide. Weave strips atop filling in lattice pattern. Fold rim over strips, pinch to seal; flute edges. (Can be prepared 5hours ahead. cover and refrigerate) Let dough rise in warm draft-free area 30 minutes.

Preheat oven to 350. Lightly brush dough with glaze. Bake until golden brown, 40-45 minutes.