In a large microwave-safe bowl, combine white chocolate and butter.

Microwave on high for 1-2 minutes, stirring at 30-second intervals, until chocolate and butter are melted and smooth.

Whisk in 1 1/2 c. sugar, eggs, orange zest, 1 tsp. vanilla, and food coloring, mixing until blended.

Stir in the 1 1/2 c. flour.

Spread batter into a greased 9x13-inch pan.

In a small mixing bowl, beat cream cheese and remaining 1/4 c. sugar until smooth.

Add egg yolk and remaining 1 tsp. vanilla extract, beating until smooth.

Beat in remaining 1 tbsp. flour.

Drop the cream cheese mixture by spoonful over the orange batter. Gently swirl with a knife or toothpick.

Bake at 350 degrees for 25-30 minutes, or until a toothpick inserted near the center comes out clean, and edges are golden brown.

Cool completely in pan on a wire rack. Cut into squares.