4 large eggs, separated
1/2 cup (60g) superfine sugar
3 Tbl (40g) all-purpose flour
1 2/3 cups (425g) strained Greek-style yogurt
grated zest of 1 unwaxed lemon ( I used Meyer lemons)
juice of one lemon
Optional Orange Syrup:
2/3 cup (160mL) water
1 1/4 cups (250g) sugar
1 Tbl. (15mL) lemon juice
grated zest of one unwaxed orange
Beat the egg yolks with the sugar to a thick, pale cream. Beat in the flour, then the yogurt, lemon zest, and lemon juice until it is thoroughly blended.
Whisk the egg whites until stiff and fold them into the yogurt mixture. Pour this into a round, nonstick baking tin (about 9 inches [22 cm] in diameter), greased with butter. Bake in an oven preheated to 350F° (175 C°) for 50-60 minutes, until the top is brown. It will puff up like a soufflé and then subside.
Turn out onto a serving plate, and serve warm or cold.
If you are making the syrup, boil the water with the sugar, lemon juice, and grated orange zest for 3-5 minutes. Let it cool, then chill in the refrigerator.