Build the sauce: Preheat the oven to 350°F. In a saucepan over medium-low heat, warm the olive oil. Add the garlic and cook for 2–3 minutes, until lightly golden and fragrant.
Simmer:
Squeeze or mash the tomatoes directly into the saucepan to break them up. Add the vegetable broth, rosemary, chili flakes, and coconut sugar.
Bring to a gentle simmer, cover, and cook for 20 minutes. Stir once halfway through and once at the end.
Add pasta and spinach:
Fold the dry pasta directly into the sauce and cook for 2 minutes, then remove from heat.
Fold in the spinach and season with salt and black pepper.
Bake:
Transfer everything to a small casserole dish. Bake for 6–8 minutes, until the sauce thickens and lightly caramelizes around the pasta.
Finish:
Remove from the oven and drizzle lightly with olive oil before serving.
