Serve this margarita for a party—you can make the raspberry mixture up to a day ahead, then simply add tequila and triple sec and blend with crushed ice before serving. Add a sugar rim and fresh raspberry garnish, and call it this summer's signature cocktail.
In a blender, combine raspberries, lime juice, and sugar (you may need to do this in batches). Whirl until puréed. Rub purée through a fine strainer set over a glass measure; discard seeds. Stir in tequila and triple sec.
Put half of the crushed ice into the blender with half of the raspberry mixture. Whirl until blended. Repeat with remaining ice and raspberry mix.
If desired, rub rims of 8 glasses (8 oz. or smaller) with lime wedge. Pour a thin layer of sugar into a shallow dish; dip glass rims into sugar. Pour margaritas into glasses and serve cold.
Note: Nutritional analysis is per serving.
Make the raspberry purée up to 1 day ahead. Refrigerate airtight, then mix cocktails just before serving.