Begin by preheating your oven to 350 degrees F. Grease and flour a 9x5-inch loaf pan; set aside.
In a small bowl, prepare the topping by whisking together the flour, sugar, and cinnamon. Set aside.
Then, for the bread, in a large bowl whisk together the flour, baking soda, baking powder, and salt.
In a medium size bowl, with a handheld (or electric mixer) beat the softened butter about three minutes until it's light and airy. Add the sugar and beat about four minutes until it's well incorporated. Next, add the eggs one at a time, mixing in the first one before adding the second. Finally, beat in the pure maple syrup, sour cream, and the vanilla.
Now gently incorporate the wet ingredients into the dry. Mix until just combined, being careful not to overmix. The final mixture will be more the consistency of dough rather than runny like cake batter.
Spread the mixture into your prepared loaf pan.
Finally, sprinkle the flour, sugar, and cinnamon mixture evenly over the top of the loaf.
Bake at 350 degrees F for 55-60 minutes. The loaf is done when a toothpick (or wood skewer) inserted near the center comes out clean.
Allow the loaf to cool in the pan for about 20 minutes. Gently run a butter knife around the edge of the pan to loosen the loaf. Remove the loaf from the pan to finish cooling.