Sauté the aromatics: In a large pot over medium heat, warm the olive oil and butter. Add the onion with a pinch of salt. Cook, stirring occasionally, until soft and translucent, about 6–8 minutes. Stir in the garlic and cook 30 seconds, just until fragrant.

Build the base: Add tomato paste and cook, stirring, for 1–2 minutes to caramelize slightly. This deepens the flavor and tames bitterness.

Add tomatoes and broth: Pour in the canned tomatoes (with juices) and the broth. If using whole peeled tomatoes, break them up with a spoon. Stir in sugar, oregano, basil, and red pepper flakes if using.

Simmer: Bring to a gentle boil, then reduce to a simmer. Cook uncovered for 20–25 minutes, stirring now and then. The flavors will meld and the soup will thicken slightly.

Blend: Turn off the heat. Use an immersion blender to puree until smooth. For extra silky texture, blend in batches in a countertop blender, venting the lid. Return to the pot.

Add cream and season: Stir in the heavy cream. Taste and adjust with salt and black pepper. If the soup is too thick, splash in a bit more broth; if too thin, simmer a few minutes more.

Make the grilled cheese: While the soup simmers, spread butter on one side of each bread slice. Sprinkle a tiny pinch of garlic powder over the butter if you like. Heat a skillet over medium. Place two slices, buttered side down, top with cheese, then close with the remaining slices, buttered side up.

Cook to golden: Grill 2–3 minutes per side, pressing gently, until the bread is crisp and the cheese melts. Reduce heat if browning too fast. Transfer to a cutting board and let rest 1 minute.

Cut into croutons: Slice each sandwich into 1-inch cubes with a sharp knife or serrated knife. Try not to squish them; a gentle sawing motion works best.

Serve: Ladle soup into bowls. Top generously with grilled cheese croutons. Finish with a drizzle of good olive oil, a few basil ribbons, or Parmesan if desired.