In a large saucepan, heat 1/4 Oil over medium heat. Make sure the pan is heavy-bottomed, like a cast iron or similar.
On a cutting board, dice 1 onion and mince 4 garlic cloves.
Add the diced onion and minced garlic to the warm saucepan and sauté for 5 minutes or until soft and tender.
Wash 2 tomatoes and then on a cutting board, dice the tomatoes. They don't have to be perfect, just roughly chopped is fine. To the saucepan, add the diced tomatoes and sauté an additional 3-4 minutes. Additionally, wash and then dice the red peppers, adding them to the saucepan to sauté. Season with salt, pepper, Thyme and 1 tsp Italian seasoning.
Transfer the cooked ingredients to a blender and blend until smooth. You can also use an emersion blender but make sure to use a tall container when blending so the sauce does not splash all over.
Replace the sauce in the saucepan and set aside.
Wash all of the vegetables and then prep each. Prepping ahead of time helps to keep the stress low when laying out the slices in the pan.
On a cutting board, peel (if desired) and then slice the eggplant into 1/4-inch slices. Not too thin, but thin enough that they aren't paper. Using a mandolin helps as well.
On a cutting board, use a sharp serrated knife to slice the tomatoes to 1/4-inch thick.
Lay the saucepan next to the cutting board, on a trivet, and then begin layering the sliced vegetables. Lay an eggplant, tomato, and then zucchini, repeating the pattern down one length of the saucepan. Then turn the pattern and continue layering the slices on the sauce until all slices are used.
Preheat the oven to 350 degrees Fahrenheit and then bake the Ratatouille for 30 minutes, covered with a piece of parchment with a hole cut in the center.
Remove the parchment paper and bake the Ratatouille for an additional 15-30 minutes, or until browned.
Remove the Ratatouille from the oven and let rest for 30 minutes before serving.
Notes
Make sure the eggplant, zucchini and tomatoes are the same size to keep the aesthetic of traditional Ratatouille.To cut the hole, fold the parchment in quarters and cut the center corner with a scissors.Traditionally, this dish is made in a circle dish, but it can also be made in a square or rectangle pan.
Keyword French Ratatouille, From scratch Ratatouille, Homemade Ratatouille, Ratatouille