Preheat oven to 350°F. Grease 9" round cake pan with at least 2" high sides. Line base with a circle of parchment paper. Topping: In a pot, melt butter, add corn syrup and brown sugar, whisking until smooth. Spread over base of prepared pan. Sprinkle with pecans. Streusel: In bowl, combine sugars, flour and cinnamon. Using a pastry blender or knives, cut in butter until mixture is very crumbly. Set aside. Cake: Combine yogurt and baking soda; set aside. In a separate bowl, combine flour, baking powder and salt. In a large bowl using electric beaters, cream butter with sugar and eggs, beating well after each addition. Add vanilla. With mixer on low, add the flour and yogurt mixtures, starting and ending with the flour mixture. Bake for 45 minutes or until a tooth pick inserted in centre comes out clean. Cool on rack for 3 minutes. Run small paring knife around edges of cake to loosen and remove cake from pan.