Preheat Oven & Prepare Pan: Preheat to 350°F (175°C). Grease and flour a 9×5-inch loaf pan or a bundt pan.
Mix Dry Ingredients: In a bowl, whisk together flour, baking powder, salt, and cinnamon.
Cream Butter & Sugar: In a large bowl, cream butter and sugar until light and fluffy. Beat in eggs one at a time, mixing well after each addition. Stir in vanilla.
Combine Dry & Wet: Gradually add dry ingredients, alternating with milk, starting and ending with flour. Mix until just combined—do not overmix.
Add Brown Sugar (Optional): If using, gently swirl brown sugar into the batter for a cinnamon-sugar ripple effect.
Bake: Pour batter into prepared pan, smooth the top, and bake 50–60 minutes or until a toothpick inserted in the center comes out clean.
Cool: Let the cake cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.
