Preheat your oven to 400ºF (200ºC). Lightly grease a 10-inch cast-iron skillet with olive oil and sprinkle 1 cup of panko bread crumbs evenly across the bottom.

In a medium skillet, heat 2 tablespoons of olive oil over medium heat. Add the sliced red onions and sauté until softened and translucent, about 4-5 minutes. Incorporate minced garlic and crushed red pepper flakes, stirring for an additional minute until fragrant. Pour in ½ cup of dry red wine, cooking until nearly evaporated, about 1-2 minutes, and then spread this mixture evenly in the prepared skillet.

Slice the butternut squash, russet potatoes, zucchini, and tomatoes into approximately 1/4-inch thick pieces. Arrange these vegetables in the skillet in circular layers, alternating between potato, tomato, squash, and zucchini.

Drizzle the layered vegetables with fresh lemon juice. Sprinkle a mix of herbes de Provence, sea salt, and coarsely ground pepper over the top. Cover tightly with aluminum foil and bake for about 1 hour, until the vegetables are almost tender.

While baking, mix 1 cup of grated Gruyere cheese, ½ cup of panko bread crumbs, and 2 tablespoons of melted clarified butter in a small bowl. This will add a rich, crispy crust.

After an hour, remove the foil and sprinkle the cheese and breadcrumb mixture over the partially cooked vegetables. Bake uncovered for an additional 15 minutes, until the cheese is melted and golden brown.

Once baked, let the Vegetable Tian rest for at least 10 minutes before slicing and serving.