Heat oil in a skillet over medium-high heat. Add onion chunks, garlic and ginger; cook for 2 minutes. Add tomatoes and cook for approximately 5 minutes. When tomatoes are cooked enough and become paste-like; add garam masala, coriander powder (or curry powder), cardamom and tumeric; stirring well.
Add mixed vegetables and cook on low heat until vegetables are soft and tender. Add coconut milk and mix well. Simmer for 1 minute. Add cilantro, cover and turn off the heat.