1 medium red onion, chopped
Kosher salt, freshly ground pepper
2 tablespoons tomato paste
4 cups vegetable broth
Heat 4 Tbsp. butter in a Dutch oven or medium stockpot over medium heat
Add onion and cook, stirring often, until softened and lightly browned around the edges, 8–10 minutes.
Season with salt and pepper.
Add tomato paste and cook, stirring to coat onion, until tomato paste is slightly darkened in color, about 2 minutes.
Add canned tomatoes, vegetable broth, thyme, bay leaf, and sugar…