Preheat oven to 350 degrees.
Combine butter and sugar in a mixing bowl and beat until light and fluffy. Add almond flour and beat for one minute. Add eggs, one at a time, beating after each addition. Add all the remaining ingredients except arrowroot. Mix until well combined. Gently fold in the arrowroot, one tablespoon at a time. Spread mixture evenly into a well greased 8x8 glass baking pan. Bake for 23 to 28 minutes until a light golden brown. Cool completely. Cut into squares.