📋 Instructions

1. 1Melt the butter — Melt the butter in a heavy Dutch oven over medium heat until it foams but does not brown, about 2 minutes at 300F (150C).
2. 2Brown the onion — Add the sliced onion and cook 8 to 10 minutes at 325F (165C) equivalent medium-low heat, stirring every 2 minutes, until the edges are golden brown and the onion slumps. Do not let it blacken; burnt edges turn the whole pot bitter.
3. 3Bloom the garlic and paste — Add the garlic and tomato paste and cook 60 to 90 seconds, until the paste darkens to brick red and smells sweet rather than raw.
4. 4Add tomatoes and broth — Crush the tomatoes by hand into the pot, add their juice, the broth, salt, pepper, and sugar. Bring to a simmer, 200F (93C) at the surface, with small bubbles at the edges.
5. 5Simmer to concentrate — Simmer uncovered 20 minutes at 200F (93C), stirring occasionally, until the liquid reduces by about a quarter and the soup coats the back of a spoon.
6. 6Blend until silky — Off the heat, add the basil, then blend with an immersion blender 60 to 90 seconds until completely smooth. If using a countertop blender, fill it halfway and vent the lid.
7. 7Finish and season — Stir in the cream if using, then taste and adjust salt. The soup should taste bright first, then sweet, with no raw tomato edge.
8. 8Serve hot — Ladle into bowls at 165F (74C) or hotter, top with torn basil, and serve with grilled cheese.