Even if you don't have an ice cream maker, you can still enjoy homemade frozen yogurt that is better than store-bought. The trick is to start with unsweetened frozen fruit and whirl it in a food processor with yogurt or buttermilk.
Combine frozen strawberries and sugar in a food processor. Pulse until coarsely chopped. Combine yogurt (or buttermilk) and lemon juice; with the machine running, gradually pour the mixture through the feed tube. Process until smooth and creamy, scraping down the sides of the workbowl once or twice. (The frozen yogurt should be firm enough to be served directly from the food processor, but if it is a little soft, let it harden in the freezer for about 30 minutes.)
Make Ahead Tip: The frozen yogurt will keep, in an airtight container, in the freezer for up to 1 week.