Pour melted butter over the bottom of a 6 quart slow cooker.
Top with brown sugar and sprinkle with nutmeg and cinnamon.
Top with peaches. You’ll need to make two layers of peaches.
In a medium-sized mixing bowl, beat butter and sugar until light and fluffy.
Mix in vanilla and eggs.
In a separate small bowl, whisk together flour, baking powder, and baking soda.
In a small bowl, combine milk and lemon juice. It will curdle.
Alternately mix in the flour and the milk/lemon juice to the butter mixture, beating well after each addition.
Pour over peaches.
Drape paper towels over top of slow cooker (to absorb any condensation during baking), then cover with lid. Cook on High until a wooden skewer inserted into center of cake comes out clean, 2 to 2 1/2 hours.
Turn off the slow cooker and let the cake sit for ten minutes and then carefully invert it onto a serving plate. Lifting and inverting the cake from the slow cooker can be tricky because they are typically very heavy, so you might want to grab a friend to help.