In a medium pot, boil tomatoes, garlic, and chilies for about 10 minutes until tomatoes are soft to touch. Set aside to cool. Fish out tomatoes, garlic, and chilies from the pot into the blender & reserve the liquid.
Blend the ingredients with little reserved liquid.
In a frying pan, heat oil over medium heat. Fry sesame seeds, cumin seeds until light brown. Keep an close eye as sesame seeds burn easily.Add red chili powder, turmeric powder to the pan and mix everything together.
Pour the sesame and spice mixture directly into the blender. Add more reserved liquid or water if needed and blend everything into a smooth consistency.
Season with salt, Nepali Sichuan pepper, and lemon juice per taste.
Store in a close lid jar in the fridge and use within 5-7 days.