Preheat oven to 350 degrees. Line an 11×7 brownie pan, or 9×9 baking pan, with parchment, using a little butter to help it stick.

In a medium bowl, combine flour, baking powder, salt, and spices and whisk together. Set aside.

In the bowl of a stand mixer or separate mixing bowl, beat butter, granulated sugar, and brown sugar on medium speed until light and fluffy. Scrape down the bowl, then mix in egg and extra yolk. Add vanilla and apple butter and mix on low until thoroughly combined. Gently stir in the flour mixture just until it’s integrated into the batter, then fold in the diced apples.

Spread the batter (it will be very thick) into the prepared pan and bake at 350 degrees for 20-25 minutes, until the edges are golden and a cake tester or toothpick comes out clean. Remove to a baking rack to cool completely before icing (you can also serve these warm, cake-style, with icing drizzled over the top).

To make the icing, whisk together sifted powdered sugar and fine salt, then add milk or water and whisk until mixture is smooth. Stir in almond butter until completely incorporated. If the icing seems too thick, add a little more liquid. You want a texture that’s spreadable but not too drippy.

Spread the icing on the cooled bars and let it set for 15-30 minutes. If desired, sprinkle with a little flaky Maldon sea salt.* Using a sharp knife, cut into 12-16 squares.