Place eggplants in a large pot and cover with water. Bring to a boil; reduce heat and simmer until tender, about 30 minutes. Drain in a colander; press out excess water with the back of a large spoon.

Heat olive oil in a large skillet over medium heat. Add onion; cook and stir until fragrant, about 3 minutes. Add green bell pepper; cook and stir until softened, 5 to 8 minutes.

Stir drained eggplant into the skillet. Add tomato sauce, salt, and pepper; cook, mashing eggplant with the back of the spoon, until flavors combine and tomato sauce darkens, about 30 minutes.