One thing that you may want to watch out for in this recipe is the sweetness. Plain yogurt can be a bit tart so you will want to test the mixture for sweetness before freezing it. You may choose to leave some bigger chunks of strawberries in.
Heat the strawberries, lemon juice and sugar and stir until the sugar has dissolved. Remove from the heat and mash the strawberries. Let cool then mix in the yogurt and test for sweetness. Chill in the fridge for a couple of hours. Freeze according to the instructions for your ice cream machine.