Step 1: Preheat your oven to 400°F (200°C). Toss the cubed apples with 2 tablespoons of melted butter and 1 tablespoon of brown sugar on a parchment-lined baking sheet.
Step 2: Roast the apples for 15-20 minutes until golden and tender. Remove from the oven and let cool to room temperature. Reduce oven heat to 350°F (175°C).
Step 3: In a large bowl, cream together the 1/2 cup softened butter and 3/4 cup granulated sugar until pale and fluffy.
Step 4: Beat in the eggs one at a time, followed by the vanilla extract.
Step 5: In a separate bowl, whisk together the flour, baking powder, and salt.
Step 6: Gradually add the dry ingredients to the butter mixture, alternating with the milk, until just combined.
Step 7: Gently fold in the roasted apples and the finely minced fresh sage.
Step 8: Pour the batter into a greased 9-inch cake pan and bake for 30-35 minutes, or until a toothpick comes out clean.
Step 9: Allow the roasted apple sage cake to cool in the pan for 15 minutes before transferring to a wire rack.