Upside Down Maple Pear Walnut Skillet Cake

Name: Upside Down Maple Pear Walnut Skillet Cake
Prep time: 25 min
Cook time: 45 min
Total time: 1 h 10 min
Cuisine: American
Ingredients: 4 Tablespoons butter; 1/2 cup light brown sugar (packed ); 1/4 cup maple syrup; 2 large pears (I used Bosc - peel, core and slice into approx 1/4-inch thick slices); 1 cup walnut pieces (lightly toastedFor the cake:); 1 and ½ cup all-purpose flour; 1 and ½ teaspoon ground cinnamon; 1 teaspoon baking soda; 1/2 teaspoon salt; 1/2 cup Greek yogurt; 1/2 teaspoon vanilla extract; 1/2 teaspoon black walnut extract; ½ cup butter (at room temperature); 1/2 cup granulated sugar; 1/3 cup maple syrup; 2 large eggs (room temperature)