12 large eggs
1/3 cup heavy cream
1 1/3 cup cubed day-old bread, crusts removed
3 Tablespoonfuls, olive oil (divided)
1 onion, cut into 1/2-inch thick strips
1 each red and green bell pepper, cored, seeded, and cut into 1/4-inch slices
1/2 cup ripe cherry tomatoes, cut in half
1 Tablespoonful unsalted butter
1/3 cup ricotta cheese (part skim)
Preheat oven to 350 degrees. In a large bowl, beat eggs, heavy cream, and salt and pepper to taste. Add bread cubes; let soak until softened, about 15 minutes.
Heat 2 Tablespoonfuls olive oil in a 10-inch cast-iron skillet over medium heat. Add onion; cook until wilted, about 4 minutes. Add peppers; cook, stirring until crisp-tender, about 5 minutes. Season with salt and pepper. Stir in tomatoes. Add butter and remaining oil to skillet; heat until foaming. Pour egg and bread mixture into pan; cook over medium heat without stirring.
Meanwhile, add ricotta by tablespoonfuls, forming little pockets on top. Continue cooking until bottom is lightly browned, about 5 minutes. There should be a few bubbles around the edges.
Once bottom crust has formed, transfer skillet to preheated oven; cook until center is firm to touch, about 15-20 minutes. To serve hot, let frittata stand at room temperature 15 minutes; to serve warm or at room temperature, let stand a little longer.