Grease a casserole dish. Put half angel food cake down on bottom. Sprinkle with rum or tiramisu liqueur to soak. Mix ricotta, milk, vanilla and white sugar together with a mixer until smooth. Pour 1/2 over the cake layer, top with other cake layer, pour the remaining cheese mixture on top. Bake for about 30-40 minutes at 350 degrees.In a skillet, melt butter, put in brown sugar, stir until blended. Add pineapple and brown for about 4 minutes. Before serving, cut slice, put on plate and top with the pineapple mixture, allowing about 2 pineapple slices for each serving. Drizzle syrup on top for extra flavor. Serve warm.