Baked Polenta with Tomato Sauce and Ricotta

Preheat the oven to 425°F. Place the tomatoes, yellow onion, and garlic in a baking pan. Bake for 45 minutes or until the garlic is soft and the skin is peeling away from the tomatoes. Remove from the oven and cool to room temperature. Remove the skin from the tomatoes and put in a saucepan. Squeeze the garlic out of the bulb and into the tomatoes. Remove the skin from the onion. Coarsely chop the onion and add to the tomatoes.
Add the olive oil to the tomatoes and puree with a handheld immersion blender until smooth. You may need to add up to 1/3 cup water if there is not enough liquid. Season with salt. Warm the tomato sauce just prior to use.
Preheat the oven to 400°F. In a medium saucepan, bring 3 cups of water to a simmer and stream in the polenta. Whisk together until there are no lumps. Cover with a lid and continue to cook over low heat for 20 minutes, stirring every 3 minutes. Be careful when you go to stir the polenta—it tends to spit out pieces of the cornmeal, which is very hot. Remove the polenta from the heat and stir in the olive oil and basil. Drop in teaspoon-size pieces of the ricotta cheese. Pour the polenta into an 8-inch square baking pan and spread evenly. Sprinkle with the Parmesan cheese and let sit for 1 hour or until the polenta has firmed up. Bake the polenta in the oven for 15 minutes or until heated through. Cut the polenta into 8 equal pieces.
Place 1/2 cup warm tomato sauce in 4 shallow bowls and top with two pieces of the polenta. Sprinkle with the chopped basil.