Preheat your oven to 350°F (180°C). This is the perfect temperature for baking our mini loaf cakes, ensuring they rise beautifully and develop a lovely golden-brown crust.
Prepare three mini loaf pans (5¾×3¾-inch) by buttering and flouring them. This step is essential to prevent the cakes from sticking, allowing for easy release after baking.
In a medium saucepan, on medium heat, combine the light brown sugar and 2 tablespoons of unsalted butter. Stir constantly until the mixture becomes smooth and bubbly, creating a delicious caramel-like base.
Once smooth, remove the saucepan from heat and stir in the Concord grapes and fresh thyme leaves. This mixture will be the sweet layer that sits atop the cake, so divide it evenly among the prepared pans.
In the bowl of a stand mixer fitted with the paddle attachment, add the remaining ½ cup of unsalted butter and granulated sugar. Beat together at medium speed for about 3 to 4 minutes, until the mixture is fluffy and light. Make sure to stop occasionally to scrape the sides of the bowl for even mixing.
After the mixture is fluffy, reduce the mixer speed to low and add the large eggs, one at a time. Beat well after each addition, ensuring that each egg is fully incorporated before adding the next.
In a separate medium bowl, whisk together the all-purpose flour, ground cinnamon, baking powder, baking soda, kosher salt, and ground nutmeg. This mixture is crucial for the cake's structure.
Gradually add the flour mixture to the butter mixture, alternating it with the low-fat buttermilk. Start and finish with the flour mixture, mixing just until combined after each addition. Be careful not to overmix!
Spoon about 1 cup of batter over the topping in each pan, smoothing it out with an offset spatula for an even surface.
Place the pans in the preheated oven and bake for 36 to 38 minutes, or until the cakes are golden brown and a wooden pick inserted into the center comes out clean. The aroma will fill your kitchen!
Once baked, let the cakes cool in the pans for 5 minutes. This resting time allows them to set before inverting.
Carefully invert the cakes onto a wire rack to cool completely. If any grapes stick to the pans, gently press them back onto the cakes.
Using a serrated knife, trim the domed bottoms off each loaf to create an even base. This step ensures they sit nicely when serving.
Serve with a generous dollop of whipped cream and garnish with fresh thyme sprigs, if desired. Enjoy your homemade Concord Grape Upside Down Mini Loaf Cakes!
