Soften the butter and combine it with the sugar in a mixing bowl with an electric mixer. Beat until fluffy. Add the flour, the baking powder and salt. Beat until crumbly.
Transfer 2/3 of the crumbs to the baking pan and pat to make an even layer. Bake 10 minutes until the surface is dry but not browned.
In a separate mixing bowl, mix together the cream cheese, white sugar, lemon zest and juice and almond extract until fluffy. Beat in the eggs until combined.
When the crust has baked, spread the cheesecake mixture evenly over the top and bake 20 minutes until the cheesecake has set.
When the cheesecake layer has baked, sprinkle the blueberries and the rest of the crust/crumb mixture over it and bake 20 minutes until the crumbs have browned.
Cool to room temperature and refrigerate at least 2 hours until the cheesecake is firm before cutting into 24 bars