Preheat an oven. In a large baking dish, combine cubed potatoes, thinly sliced onion, thinly sliced fennel, diced bell pepper, diced tomatoes, and sliced garlic cloves. Drizzle with extra virgin olive oil, then season with herbs de Provence, kosher salt, and freshly ground black pepper. Toss well, then cook.
Pat the fish dry with a paper towel, then using a sharp knife. Season the cavity of the snapper generously with kosher salt and black pepper. Place a few lemon slices inside along with the bundle of fresh herbs. Refrigerate until needed.
When the veggies are tender, add a splash of white wine vinegar, give them a good stir, then place the seasoned fish on top. Drizzle with remaining olive oil and kosher salt. Return the dish to the oven and cook until the fish is fully cooked and flakes easily.
Gently remove the skin, then pull away the flesh and place individual portions onto plates. When you’ve finished the first side, you should be able to carefully lift away the body and bones by lifting the tail end of the fish. Serve with roasted veggies, a sprinkle of fresh parsley, and lemon wedges!