In a medium pot, heat the oil over medium heat. Sauté the onion until soft. Add the pumpkin & red bell peppers. Sauté for 3 minutes.
Add the can of tomatoes, milk, and vegetable or chicken stock. Add vegetables to a blender in two separate batches and pure until smooth.
Puree directly in the pot with an immersion blender. Return to the pot and season with salt & black pepper according to taste. Heat soup again if needed.
Fresh herbs or a swirl of cream can add a nice touch. Sprinkle with toasted pepitas (pumpkin seeds) or croutons.