Toasting gives dishes a nutty undertone.
Preheat the oven to 375°. On two parchment-lined baking sheets, divide the speck, arranging in a single layer. Bake until crispy, 7 to 8 minutes. Let cool; crumble.
In a deep skillet, heat 2 tbsp. oil, two turns of the pan, over medium-high. Add the onion, sliced garlic and rosemary. Cook, stirring often, until softened, 2 to 3 minutes. Add the tomatoes and beans; season with salt and pepper. Cook, stirring often, until the tomatoes slump (they soften and the skin shrivels), 3 to 4 minutes. Add the stock; let the ragu simmer until ready to serve.
Char the bread on both sides directly over the gas flame on a stove using tongs or, after you remove the speck, preheat the broiler and toast the bread. Rub with the halved garlic, drizzle with oil and season with salt.
Shingle 2 slices of bread in each of 4 shallow bowls.
Add the greens to the bean ragu. Cook, stirring often, until wilted, about 3 minutes. Add the lemon juice; ladle over the toasts. Top with the speck and cheese.