Line a strainer or colander with 4 layers of cheesecloth or 1 coffee filter; place over a bowl. Place yogurt in prepared strainer; cover yogurt with sides of cheesecloth. Refrigerate 2-4 hours., Remove yogurt from cheesecloth to a bowl; discard strained liquid. Add sugar and vanilla to yogurt, stirring until sugar is dissolved., In a small microwave-safe bowl, combine cold water and lemon juice; sprinkle with gelatin and let stand 1 minute. Microwave on high for 30 seconds. Stir and let mixture stand 1 minute or until gelatin is completely dissolved; cool slightly. Stir gelatin mixture into yogurt. Cover and refrigerate until cold, about 40 minutes. , Pour yogurt mixture into cylinder of ice cream freezer; freeze according to the manufacturer’s directions., Transfer frozen yogurt to a freezer container. Freeze 2-4 hours or until firm enough to scoop.