Heat oven to 350°F. Grease a 9x13-inch baking pan.
Whisk cake mix, milk, oil, and liquid eggs until smooth, about 2 minutes.
Stir together brown sugar, cinnamon, nutmeg, and melted butter to make a thick swirl.
Pour batter into the pan. Spoon cinnamon mixture over the top and marble with a knife.
Bake until golden and a tester comes out clean, 28–32 minutes. Cool 10 minutes.
Poke holes all over the warm cake with the handle of a wooden spoon.
Warm the sweetened condensed milk slightly, then pour evenly over the cake to soak. Cool completely.
Beat cream cheese until smooth. Mix in powdered sugar, vanilla, and salt.
Drizzle in heavy cream to reach a pourable glaze. Spread over the cooled cake.
Finish with pecans and a light caramel drizzle, if using. Slice and serve.