Heat a large skillet over medium heat. Add 2 tablespoons of olive oil. Once hot, add 1 diced brown onion, 1 diced bell pepper, and 2 minced garlic cloves. Cook until the vegetables are soft and the onions are translucent, about 5 minutes.

Stir in 1 tablespoon of chili powder, cook for another minute until fragrant.

Add 2 tablespoons of tomato purée, 1 can of chopped tomatoes, and 1 can of drained and rinsed red kidney beans to the skillet. Let the mixture simmer for about 20 minutes, stirring occasionally, until thickened.

While the chili cooks, prepare the taco assembly ingredients. Shred some lettuce and dice fresh tomatoes. Grate 100 grams of cheddar cheese.

Warm 8 tortillas by lightly toasting them in a dry skillet or microwave just before serving.

To assemble the tacos, spoon the vegetarian chili onto each warmed tortilla. Top with shredded lettuce, diced tomatoes, grated cheddar cheese, and a dollop of sour cream.

Serve immediately.