-
Preheat your oven to 350°F (175°C) and place the rack in the center.
-
Grease the bottom and sides of a solid 8-inch or 9-inch round cake pan with butter or non-stick spray.
-
Cut a circle of parchment paper to fit flat on the bottom of the pan, press it down, and grease the top of the parchment paper too. (This guarantees zero sticking when you flip it on camera).
-
In a small bowl, whisk together the melted butter, brown sugar, heavy cream, and ¼ tsp salt until smooth.
-
Pour the mixture onto the parchment paper at the bottom of the pan and spread it into an even layer.
-
Arrange your walnut halves neatly in concentric circles (flat-side up, rounded pretty-side facing down into the caramel) so the top looks like a bakery masterpiece once flipped.
-
In a medium bowl, whisk together the flour, baking powder, and ¼ tsp salt. Set aside.
-
In a large bowl, beat the softened butter and white sugar with a hand mixer (or whisk vigorously) for 2 full minutes until pale, light, and creamy.
-
Add the eggs one at a time, beating well after each addition until completely smooth, then mix in the vanilla extract.
-
Add half of the flour mixture and mix on low speed just until combined.
-
Pour in all ½ cup of milk and mix gently.
-
Add the remaining flour and fold gently with a spatula just until no white streaks remain.
-
Do not overmix!
-
Spoon the thick batter gently in dollops over the walnuts so you don't shift your neat walnut pattern, then smooth the top gently with a spatula.
-
Bake for 32 to 38 minutes until the top is golden brown and a toothpick inserted into the center comes out clean (a few moist crumbs are fine, no wet batter).
-
Remove the cake from the oven and let it cool on the counter for exactly 10 minutes. (If you flip immediately, the caramel is too runny; if you wait longer than 15 minutes, the caramel cools and sticks to the pan!)
-
Run a thin butter knife gently around the inside edge of the pan to loosen the sides.
-
Place your serving plate upside-down over the top of the cake pan, hold both together firmly with oven mitts, and flip it over in one confident motion.
-
Leave the pan resting upside-down on the plate for 30 seconds so gravity pulls every drop of caramel down
-
Lift the pan off and peel away the parchment paper while warm!
