Step 1: Reduce Apple Cider - Pour fresh apple cider into a wide, shallow pan. Heat over medium-high for 10-15 minutes until reduced by half and thickened. Cool completely.

Step 2: Prepare Wet Ingredients - In a bowl, combine olive oil, granulated sugar, brown sugar, and sour cream. Whisk until smooth, then add cinnamon and salt.

Step 3: Combine Ingredients - Gradually whisk in the reduced apple cider into the wet ingredients until well incorporated.

Step 4: Mix Dry Ingredients - In another bowl, sift together flour, baking powder, and baking soda. Mix to distribute evenly.

Step 5: Combine Wet and Dry Mixtures - Slowly add the dry mixture to wet ingredients, gently folding until just combined.

Step 6: Prepare Baking Dish - Line an 8x8 inch baking dish with parchment paper, pour in the batter, and tap lightly to release air bubbles.

Step 7: Bake - Preheat oven to 375°F (190°C) and bake for 22-25 minutes until a toothpick comes out clean.

Step 8: Top Cake - Brush warm cake with melted butter and sprinkle with cinnamon sugar.