Preheat the OvenSet your oven to 375 degrees F (190 degrees C) to get it warm and ready for baking the ratatouille.
Blend the Sauce In a blender, combine the drained diced tomatoes, olive oil, balsamic vinegar, herbs de Provence, and garlic. Puree the mixture until smooth and adjust with salt and pepper to taste.
Prepare the Casserole Dish Spread the smooth sauce in a thin, even layer across a medium-sized round or oval casserole dish, ensuring it's well coated.
Arrange the VegetablesLayer the sliced tomatoes, zucchini, eggplant, and onion in a spiral pattern, alternating them as you go. Make sure the eggplant pieces are cut into quarters for even cooking.
Dress and Season Drizzle olive oil over the arranged vegetables, then sprinkle with sea salt and black pepper to season.
Bake to Perfection Place the casserole dish in the oven and bake for 30 to 35 minutes. Look for the veggies to become tender and the sauce to bubble at the edges.
Notes
For a visually stunning presentation, maintain even thickness when slicing your vegetables.
To remove bitterness from eggplant, sprinkle salt on slices and let sit for 10 minutes before rinsing.
This dish tastes even better the next day as the flavors meld together.