To Make the Marinara Sauce:
Pour 2 tablespoons of olive oil into a saucepan over medium heat.
Add the onions and red peppers to the pan and sauté for 5 minutes.
Mix in the garlic, tomatoes, tomato paste, oregano, and basil.
Simmer on low heat for about 30 minutes.
Place the marinara in a blender or use an immersion blender to process until you have a smooth sauce. If you prefer a chunkier sauce, process it for a shorter time.
Check seasonings and add coconut sugar, salt, and pepper as needed. Set the sauce aside.
Prepare the Eggplant:
Preheat the oven to 400°F (204°C).
Place the eggplant slices on a parchment-covered sheet pan.
Brush the slices with olive oil and sprinkle with salt and pepper.
Bake in the oven for 10 minutes, flip, and cook for another 10 minutes until golden and tender. Remove from oven.
Assemble the Eggplant Parmesan:
Reduce the oven temperature to 375 degrees.
While the eggplant is baking, place the ricotta, egg, Parmesan, parsley, ½ teaspoon salt, and ½ teaspoon pepper in a bowl and mix thoroughly.
Pour a thin layer of marinara sauce to cover the bottom of a baking dish.
Depending on how many servings you are making, place 8 to 10 of the larger eggplant slices in the dish.
Place a slice of mozzarella on each piece of eggplant. Slice the mozzarella, so you have two slices per serving.
Spoon a scoop of the ricotta mixture onto each slice.
Lay another slice of eggplant on each serving.
Pour a spoonful or two of sauce over each stack.
Add another slice of mozzarella and a dollop of ricotta to each serving.
Place the dish in the oven and bake for 15 to 20 minutes.
Turn the broiler on for a few minutes to brown the top a bit, then remove from the oven.
Garnish each serving with fresh basil and extra marinara sauce.
Plating tip: Ladle some sauce onto the plate, place a stack of eggplant on top, and garnish with fresh basil.