Step 1

FOR THE POLENTA: Lightly grease 8-inch square baking pan. Heat butter and oil in Dutch oven over medium heat until butter is melted. Add garlic and cook until lightly golden, about 4 minutes. ­Discard garlic.

Step 2

Add water, salt, and pepper to butter mixture. Increase heat to medium-high and bring to boil. Add cornmeal in slow, steady stream, whisking constantly. Reduce heat to medium-low and continue to cook, whisking frequently and scraping sides and bottom of pot, until mixture is thick and cornmeal is tender, about 20 minutes.

Step 3

Off heat, whisk in Pecorino and half-and-half. Transfer to prepared pan and let cool completely on wire rack. Once cooled, cover with plastic wrap and refrigerate until completely chilled, at least 3 hours.

Step 4

FOR THE RED SAUCE: Process tomatoes and their juice in blender until smooth, about 30 seconds. Heat 1 tablespoon oil in large saucepan over medium heat until shimmering. Add onion, cut side down, and cook without moving until lightly browned, about 4 minutes. Add pureed tomatoes, tomato sauce, Pecorino, sugar, salt, garlic powder, and remaining 3 tablespoons oil. Bring mixture to boil, reduce heat to medium-low, and simmer until sauce is slightly thickened, about 15 minutes. Remove from heat, discard onion, cover, and keep warm.

Step 5

Adjust oven rack to middle position and heat oven to 375 degrees. Line rimmed baking sheet with parchment paper, then grease parchment. Cut chilled polenta into 6 equal pieces (about 4 by 2 2/3 inches each). Place on prepared sheet and bake until heated through and beginning to brown on bottom, about 30 minutes. Serve each portion covered with about 1/2 cup red sauce.