Preheat your oven to 425 degrees F. Spread the halved cherry tomatoes cut-side up on a rimmed baking sheet. Drizzle with 1 tablespoon of olive oil, sprinkle with 1/4 teaspoon of salt, and toss to coat. Roast for 20 minutes until the tomatoes are shriveled, slightly caramelized, and most of the liquid has evaporated. Set them aside and reduce the oven to 375 degrees F.

While the tomatoes roast, warm 2 tablespoons of olive oil in a large skillet over medium heat. Add the sliced garlic and cook for 1 to 2 minutes, stirring often, just until it turns golden at the edges. Do not let it burn. Add the spinach in two or three handfuls, stirring between additions, and cook for 2 to 3 minutes until fully wilted. Remove from heat.

Add the drained white beans to the skillet with the spinach and garlic. Stir in the lemon juice, thyme, red pepper flakes if using, the remaining 3/4 teaspoon of salt, and black pepper. Gently fold in the roasted tomatoes. Taste and adjust salt if needed.

Transfer the bean and tomato mixture to a 2-quart baking dish and spread it into an even layer.

In a small dry skillet over medium heat, warm the remaining 1 tablespoon of olive oil. Add the breadcrumbs and stir constantly for 2 minutes until they are golden and toasted. Remove from heat and stir in the Parmesan if using. Scatter the toasted crumbs evenly over the top of the casserole.

Bake uncovered at 375 degrees F for 20 to 25 minutes, until the filling is bubbling around the edges and the breadcrumb topping is deep golden brown. Let it sit for 5 minutes before serving.