In a large bowl, whisk together the flour, salt, sugar and lemon zest.
Cut in the butter and blend in with your fingers until mixture resembles cornmeal.
Add egg yolk and cold water.
Mix until dough comes together to form a shaggy ball (dough may be dry). Cover in plastic wrap and let chill for half an hour.
Preheat oven to 375 degrees.
Butter a 8″ square pan generously. After your dough has chilled, remove from fridge and roll out on a lightly floured surface. You want the dough to be about 1/4″ thick. Place the square pan on your rolled out dough and trace around the edges of the pan with a knife so you now have a square of dough. Place dough square in the pan and prick all over with a fork.
Bake crust for 25-30 minutes, until golden. Remove from oven and let cool briefly while you make the filling.
To make the filling, In a blender or food processor, combine the eggs, sugar, yogurt and vanilla. Blend until smooth then add cornstarch and pinch of salt and blend again. Pour filling into crust.
Place your strawberry jam into a small plastic ziploc bag. Snip off the tip of the bag and swirl jam around the cheesecake.
Lower oven temperature to 350 and bake cheesecake for 35-40 minutes. The cheesecake will begin to start separating from the sides of the dish and turn a light golden color. The top should be set but there should still be a slight jiggle. Note that when the cheesecake has finished cooking, the jam will have sunk into the cheesecake creating crevices. These aren’t terribly attractive but you cover everything up anyway with strawberries at the end.
Chill cheesecake for 2 hours. Arrange sliced strawberries all over the top of the cheesecake. Zap 2 tbsp jam in the microwave and brush on the strawberries with a pastry brush – this will give the berries some shine. Carefully cut cheesecake into bars and serve.