1Prepare the streusel: In a bowl, mix flour, dark brown sugar, cinnamon, and butter using a fork until crumbly with no dry flour left. Set aside.
2Preheat oven to 175°C (350°F). Grease and line an 8.5x4.5 inch loaf pan with parchment paper.
3Sift flour, baking powder, baking soda, and salt in a bowl. Set aside.
4In a large bowl, beat butter and sugar on high speed for 3 minutes until light and fluffy.
5Add eggs one at a time, mixing on medium speed until well combined.
6Add half of the flour mixture on low speed, then mix in sour cream, oil, and vanilla. Add remaining flour mixture and mix just until combined. Scrape the bowl.
7Transfer half of the batter to another bowl and mix in ground cinnamon.
8Alternate scooping plain and cinnamon batter into the pan. Use a butter knife to swirl.
9Sprinkle streusel evenly over the top.
10Bake for 65 minutes or until a cake tester comes out clean.
11Let cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.
Ingredients
60 g all-purpose flour
50 g dark brown sugar
0.5 tsp ground cinnamon
40 g unsalted butter, room temperature
270 g all-purpose flour
0.75 tsp baking powder
0.5 tsp baking soda
0.5 tsp salt
100 g unsalted butter, room temperature
200 g granulated sugar
2 large eggs, room temperature
200 g sour cream, room temperature
30 g vegetable oil
1.25 tsp vanilla extract
1.25 tbsp ground cinnamon
Equipment
bowlforkwhiskspatula8.5x4.5 inch loaf panparchment papercake testerwire rack