In a large pot, heat the olive oil over medium heat. Add the diced onion and cook until softened and caramelized, about 8-10 minutes. Stir occasionally to prevent burning.

Add the minced garlic, salt, black pepper, and red pepper flakes (if using) to the pot. Cook for an additional 1-2 minutes until fragrant.

Stir in the gochujang and cook for another minute to toast the paste slightly.

Add the diced tomatoes (with their juice), vegetable broth, sugar, and apple cider vinegar. Bring to a simmer and let cook for 15-20 minutes, stirring occasionally.

Remove from heat and use an immersion blender to puree the soup until smooth. If you don’t have an immersion blender, carefully transfer the soup in batches to a countertop blender.

If desired, stir in the heavy cream for a richer flavor and creamier texture.

Serve hot, garnished with fresh basil.