Preheat oven to 350 degrees. Grease and add parchment paper to a 9x11 glass baking dish.
Cut butter into small pieces. Mix with flour and powdered sugar. Go in with your hands and mix until incorporated. You should end up with a crumbly mixture like pie dough.
Pour the crust mixture into the baking dish and push down with your fingers until you've created an even layer.
Bake the crust for 20 minutes.
While the crust is baking, beat eggs. Mix in flour and sugar and add the lemon juice.
Once the crust has pre-baked, pour the filling into the crust.
Put back into the oven for 25 minutes, rotating the pan halfway through to ensure an even bake from front to back. Check the filling to make sure it's fully set up yet not overcooked.
Remove from the oven and cool on the counter for 30 minutes before placing in the fridge to fully cool.
Once cool, sift powdered sugar on top of the lemon bars.
Cut and serve. Store in the fridge in a sealed container.