Method

In food processor, whirl together fruit, sugar and lemon juice until smooth. Add yogurt; whirl until blended.

Press though sieve into 9-inch (2.5 L) square metal cake pan; freeze until almost solid, about 1-1/2 hours. Break up and pur?in food processor until smooth. Scrape into airtight container; freeze until firm, at least 4 hours. Or freeze in ice-cream machine according to manufacturer's instructions. (Make-ahead: Freeze for up to 1 week.)