3/4 cup to 1 cup of sugar (depending on how sweet your blueberries are, and how sweet you want the result to be)
1/4 teaspoon salt
1/8 teaspoon cinnamon
1 1/2 cups full fat plain yogurt (full fat yogurt is preferred, if you use low-fat or non-fat yogurt, substitute 1/4 cup of it with heavy whipping cream)
1/2 cup whole milk
1 Place the blueberries, lemon juice, sugar, salt, and cinnamon in a medium saucepan. Heat on medium heat, stirring, until all of the sugar has dissolved. While the mixture is heating, use a potato masher to mash up the blueberries. When all of the sugar has dissolved, remove from heat and let cool for 10 minutes.
If you want a smooth result, you can process the cooled mixture in a food processor, or skip, in which case you'll have pieces of blueberries which can add flavorful texture to the frozen yogurt.
2 Stir in the yogurt and milk until completely incorporated. Chill the mixture in the refrigerator for several hours (or overnight) until completely cold.
3 Process the blueberry yogurt mixture in your ice cream maker according to manufacturer's instructions (usually about 25 minutes). Serve immediately (it will be soft) or let it firm up a bit by freezing it for several hours.