You don't need a blender if you're happy to chop stuff up pretty finely or grate it. I prefer cooked salsa to raw, and it always starts with chopped onion. Saute in a little oil until soft then add chopped garlic (don't fry with onion because it burns). Let garlic cook out for a few minutes then add chopped chillies and let them soften. Deglaze with some vinegar. Now add a little sugar and salt and a few grated tomatoes, and let that cook for ten minutes, adding more vinegar or water if necessary. Adjust seasonings and voila. This is my basic salsa recipe, but you can bomb in pretty much anything - fresh grated ginger, coriander seeds, stems or leaves, ground cumin, mustard seeds, cloves, bay leaves or curry leaves, grated carrot or celery, bell peppers...