Preheat your oven to 325 degrees. Grease and flour a 9” round cake pan.

In a small bowl, stir together 3 tablespoons melted butter, 1 tablespoon maple syrup, and ⅔ cup sugar. Pour/spoon this mixture into your greased cake pan.

Place the chopped rhubarb on top of the butter-sugar mixture in the pan. Sprinkle 1 ½ Tbsp sugar on top. Set aside.

In a large bowl, cream 6 Tbsp softened butter until fluffy. Add ¾ cup sugar and 1 Tbsp maple syrup and mix well for about 3 minutes. Beat in 2 egg yolks along with 1 Tbsp vanilla extract. Set aside.

In a separate small bowl, whisk together 1 cup + 2 Tbsp flour with the baking powder and salt.

Back to the creamed butter mixture. While mixing on low speed, alternately add the flour mixture with ¼ cup milk, beating well after each addition and scraping the sides of the bowl as needed. Set aside again.

In a separate medium-sized bowl, beat the 2 egg whites along with ¼ tsp cream of tartar until stiff peaks form. Gradually fold the egg mixture into the batter. Do not overbeat. The mixture should be light and fluffy at this point.

Gently spoon the batter mixture over the rhubarb in the pan.

Bake for 50-60 minutes or until the cake springs back when you lightly touch it. Cool on a wire rack for about 10 minutes before inverting onto a serving plate.

Serve with whipped cream (optional)