01 -
Preheat the oven to 177°C. Line an 8-inch (20 cm) square baking pan with parchment paper.
02 -
Beat softened butter and brown sugar on medium-high speed for about 1 minute until combined.
03 -
Add vanilla extract and beat for 30 seconds until fully incorporated.
04 -
Add flour, baking powder, salt, and oats. Mix on medium speed until the mixture becomes crumbly.
05 -
Press slightly more than half of the crumble mixture evenly into the bottom of the prepared pan to create the crust.
06 -
Bake the crust for 12 minutes, then remove from the oven.
07 -
Whisk together the sweetened condensed milk, lemon juice, and lemon zest until smooth and thickened.
08 -
Pour the lemon filling evenly over the pre-baked crust.
09 -
Sprinkle the remaining crumble mixture evenly over the lemon filling.
10 -
Return the pan to the oven and bake for an additional 22 to 25 minutes, until edges are lightly golden and the center is set.
11 -
Allow the pan to cool completely on a wire rack.
12 -
Lift the bars out using the parchment paper and slice into 16 squares.
13 -
Store at room temperature for up to 2 days or refrigerate for up to 1 week.