In a bowl, whisk together flour, almond meal, baking powder, baking soda, ginger, cinnamon, nutmeg, cloves, and salt.
In another large bowl, beat the butter and brown sugar together until fluffy.
Add the egg and continue to beat until well combined.
Mix the honey, milk, and orange zest into the butter mixture.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
Spread the batter evenly into the prepared pan.
Bake for 20-25 minutes or until a toothpick inserted into the center comes out clean.
While the Lebkuchen is baking, whisk together powdered sugar, melted butter, and dark rum. Add 1 teaspoon warm water if needed to create a pourable consistency.
Let the Lebkuchen cool in the pan for about 10 minutes, then drizzle the icing over the top and spread to form a smooth layer.
Allow it to cool completely before cutting into squares to serve.