• Preheat the oven to 350 degrees.
• Grease a 10-inch x 5-inch loaf pan and set it aside.

Prepare the batter:

• In a large mixing bowl, combine the butter and the sugar. Cream them together until well combined.
• Next, you’ll add in one egg at a time. Using a hand mixer beat the eggs into the creamed sugar and butter mixture.
• In a separate bowl, combine the flour, baking powder, baking soda, and salt. Whisk together.
• Once the dry ingredients are well combined you will begin by adding a small amount of the dry ingredients into the butter, egg and sugar mixture.
• Next, you will add a small amount of the sour cream and gently fold it into the batter. Alternative adding the dry ingredients and the sour cream until everything is well combined in in one bowl.

Prepare the cinnamon filling:

• In a separate small bowl, combine the melted butter, cinnamon, sugar, and flour. Mix until well combined. Set aside.

Prepare the oat topping:

• Grab another small bowl and add the oats, cinnamon, melted butter and brown sugar. Mix until well combined. Set aside.

Assemble the coffee cake loaf:

• Grab the greased loaf pan and add about half of the batter into the pan. Spread it out evenly using a spatula.
• Next, you’ll add a layer of the cinnamon filling. I used a spoon to gently dollop small amounts of the filling across the batter. Then you’ll want to use a toothpick to gently swirl the filling around, so it creates a beautiful swirl pattern when it bakes.
• Top with the remaining batter and spread it out evenly with a spatula.
• Bake for 40 minutes. Top with the oat topping and cook for the remaining 10 minutes. Bake time is roughly 50 minutes total or until fully cooked through.
• Let the entire loaf cool on a wire rack before slicing.