- Olive oil, as needed
- ½ onion, finely diced
- 3 cloves garlic, minced
- 1 (15-ounce) can crushed tomatoes
- ½ teaspoon chili flakes (optional, to taste)
- Kosher salt, to taste
- 3 sprigs thyme
- 3 medium all-purpose potatoes, parboiled and cooled, sliced into rounds about ⅛ inch thick
- 2 fennel bulbs, sliced into rounds about ⅛ inch thick
- 2 medium thin eggplants, sliced into rounds about ⅛ inch thick
- ½ cup grated gruyere cheese (optional)
- Black pepper, to taste
- Fennel fronds, roughly chopped, as garnish
In a medium saucepan, sauté onion and garlic in olive oil. When the onions begin to turn translucent and the garlic is fragrant with no color, add in tomatoes, chili flakes, ½ teaspoon of salt and sprigs of thyme. Cook over medium-low heat, covered, for 10–15 minutes.
Preheat oven to 375 degrees.
Prep all vegetables, organize into separate piles. In a 9-inch pie dish (or rectangular baking dish) place a layer of sauce on the bottom; this should fill about ¼ of the dish. If using cheese, add that layer next. Layer sliced vegetables on top, alternating between potato, fennel and eggplant. Season with salt and pepper to taste and a generous drizzle of olive oil.
Bake for about 1 hour, or until the vegetables are tender and lightly roasted.
Garnish with fennel fronds and additional cheese.