Place the ice in a blender and pulse several times to begin breaking it up. Add the raspberries, club soda, lemonade concentrate, 1 tablespoon of the lemon juice, and the tequila and blend until thick and smooth, about 30 seconds.
Pour the remaining 1 tablespoon lemon juice into a small saucer. In another saucer, pour a thin layer of salt (table salt is fine, kosher salt even better). Dip the rims of four margarita glasses in the lemon juice, and then in the salt. Pour the margarita mixture into the salted glasses and serve.