Preheat oven to 350 F (180 C) and line a 9x9 inch square baking pan with parchment paper. Allow parchment paper to droop over the sides.
In a large bowl hand whisk together sifted flour, salt, baking powder and nutmeg. Set aside.
Combine melted butter, sugar and sunflower butter in a medium bowl Stirring with whisk until smooth.
Melt white chocolate in a double broiler or in 30 second microwave intervals stirring in between until mostly melted.
Add melted white chocolate to the sunflower butter sugar bowl. Fold in with a spatula.
Add vanilla and eggs to sugar white chocolate mixture. Stir with whisk until combined.
Spoon wet mixture into flour mixture half at a time. Use a spatula to fold and figure eight until all ingredients combined.
Transfer blondie batter to prepared pan and level with rubber spatula.
Bake on middle rack for 25-30 minutes until a toothpick inserted into the center comes out with just a few moist crumbs.
Place tray on cooling rack and allow blondies to completely cool.
Once cooled, grab sides of parchment paper and lift the large square blondie from pan.
Place blondies on cutting surface. Cut in half to create two rectangles.
Measure and cut each rectangle into triangles of desired size. See pics for inspo.
Pipe frosting onto triangles from the top going side to side until you reach the bottom, resembling a tree.