Kefir Rhubarb Coffee Cake

Ingredients

• 4 Tbsp (1/2 stick) unsalted butter, melted + more for dish
• ¾ cup all-purpose flour, plus more for dish
• ¼ cup sugar
• ¼ cup packed light-brown sugar
• 1/4 tsp salt
• 1/4 tsp cinnamon
• For the cake: 1 ½ cups all-purpose flour
• 1 tsp baking powder
• ¼ tsp salt
• 8 tablespoons (1 stick) unsalted butter, softened
• ¾ cup sugar
• 2 eggs
• 1 tsp vanilla
• ¼ cup Lifeway Lowfat Plain Kefir
• 2 cups fresh rhubarb, sliced into ½ inch pieces