Sauté onion in olive oil until soft. Make sure your pan is properly heated before adding ingredients — you should hear a nice sizzle. Don't overcrowd the pan or things will steam instead of getting that beautiful golden color.
Add garlic and cook 1 minute.
Add tomatoes, broth, and sugar.
Simmer 15 minutes. Keep an eye on the heat — you want a gentle simmer with small bubbles, not a rolling boil. This helps develop flavor without overcooking.
Add basil and blend until smooth.
Stir in cream.
Season with salt and pepper. Always taste as you go — you can add more seasoning, but you can't take it away!