What are you putting in your salsa?
Using the blender is not your best bet. Do you have a food processor? use that, it will not liquify your tomatoes and won't add the additional air that a high speed blender will. Save that for the margaritas.
How about a simple pico de gallo? Use fresh diced tomatoes, onion, jalapeno, cilantro, lime, s&p. That's it.
You want a pureed salsa, here's a good one.
12 tomatillos, charred on the bbq
3-4 jalapenos charred
1 onion cut in 3-4 slices, charred
2 small cans stewed tomatoes, cilantro, lime juice, pinch of oregano, pulse all in the processor until smooth, s&p to taste.
(I used to use fresh tomatoes, but the quality is never consistant, so I started using canned)
I use this on fish tacos, and as a base for other salsas, also great for chips!