polenta cakes with tomato sauce

3/4 cup polenta, prepared according to package’s instructions
1 Tbsp plus 2 tsp olive oil
1 small onion, small dice
5 cloves garlic, divided, minced
Kosher salt and freshly ground black pepper
1 28-oz can peeled whole tomatoes, crushed by hand

Make the polenta:
1. Pour the prepared polenta into a square or rectangular pan. Cool and then invert onto a cutting board.
2. Cut the polenta into triangles, or whichever shape you prefer.
3. Heat 1 Tbsp of the oil in a pan over medium high heat. Sear each triangle until crisp and golden brown, about 3-5 minutes each side, depending on the thickness.

Make the sauce:
1. Heat the remaining 2 tsp oil over medium heat in a medium pot.
2. Add the onion and garlic and season with salt and pepper. Sweat until softened, about 5-7 minutes.
3. Add the tomatoes and juice to the pot. Stir and simmer over medium low heat for 20-30 minutes, until the flavors have melded but remain bright.

Spoon the tomato sauce onto a plate. Top with seared polenta. Serve with wilted baby spinach.