Preheat oven to 350°F. Grease a 9x5 inch loaf pan.
Prepare the bread batter. In a medium sized mixing bowl whisk together flour, baking powder, baking soda, cinnamon and salt.
In a large mixing bowl, combine melted butter and granulated sugar. Stir in eggs one at a time. Add milk, greek yogurt, and vanilla extract and stir to combine.
Add dry ingredients to the wet ingredients and stir gently until you have a thick batter and most of the clumps are gone.
Prepare the cinnamon streusel. Combine flour, brown sugar, cinnamon and salt in a bowl. Add the cold butter and cut in with a pastry cutter, fork or your hands until the mixture becomes crumbly. The streusel should be moist throughout with some pea-sized clumps.
Add 1/2 of the batter to the loaf pan. Top with 1/2 of the cinnamon streusel. Add the remaining batter and top with remaining cinnamon streusel.
Bake for 40-50 minutes or until a toothpick comes out clean. Allow the pan to cool slightly before carefully removing the bread. If you leave the bread in the pan too long, the bottom will start to get soggy as it cools.
Prepare the glaze. Mix powdered sugar, milk and vanilla extract in a small bowl.
Drizzle bread with the glaze and cut it into 3/4 inch thick slices