Toast the pumpkin seeds in a preheated 180 C oven for 6 to 8 minutes.
Raise the oven's temperature to 230 C.
Place the green capsicums and chillies on a baking tray. Roast for 15 to 20 minutes or until the skin blisters. Let cool a bit then pull the skin away from the flesh; discard the skin.
In a food processor or blender combine 4 tablespoons of the pumpkin seeds, coriander, garlic and the capsicums and chillies. Pulse until the contents are coarsely chopped. With the machine running, slowly add the oil and the lemon juice. Blend in the salt and pepper.
Cook pasta according to package instructions. Drain and return the pasta to the pot.
Set the pot over medium heat, add the tomatoes and the pesto. Stir well. Add more salt and pepper, if desired. Serve the pasta garnished with the remaining pumpkin seeds and lemon wedges.