Cooked Eggplant Salad

Name: Cooked Eggplant Salad
Ingredients: 3–4 large onions, diced; 6–7 tablespoons oil, divided (more if necessary); 2 medium eggplants (about 1 and 1/2 pounds or 3/4 kilogram), cubed; 8 cloves garlic, or to taste, thinly sliced; 4 medium ripe, juicy tomatoes, cubed; handful of cherry tomatoes, quartered (optional, but recommended); salt, to taste (be generous); pepper, to taste (be generous); 1–2 teaspoons brown sugar, or to taste; handful or 2 of chopped fresh parsley (optional but recommended)