Preheat oven to 350°F (175°C).
In a medium bowl, combine graham cracker crumbs, melted butter, and sugar; mix well.
Press the mixture evenly into the bottom of a 13 x 9 inch baking dish.
In a large bowl, beat the softened cream cheese and sugar together until smooth, about 2-3 minutes.
Add sour cream, vanilla extract, and lemon extract; beat until combined.
Add the eggs one at a time, mixing on low speed until just blended after each addition.
Pour the cheesecake filling over the prepared crust and smooth the top.
Bake for 45-50 minutes, until the center is almost set but still slightly jiggly.
Remove from oven and allow to cool to room temperature.
Refrigerate the bars for at least 4 hours or overnight.
Before serving, spread lemon pie filling evenly over the cheesecake bars.
Optionally, garnish with whipped cream and lemon slices.