For the Pound Cake: Grease and flour a 10-inch tube pan.
Using a mixer, cream together the butter, cream cheese and sugar until the mixture is light and fluffy. Add the eggs one at a time, beating well after each addition. Stir in the lemon and vanilla extracts. With the mixer set to low speed, gradually add the sifted flour until the mixture is smooth. Beat until just combined.
Pour the batter into the prepared pan. Place the pan in a cold oven and bake at 325°F for 1 1/2 hours, or until a toothpick inserted in the center comes out clean. Remove from the oven and allow the cake to cool in the pan for 10 minutes before turning out onto a wire rack. Cool completely before serving.
For the Sweet Potato Cheesecake: Boil the sweet potatoes for 40 to 50 minutes, or until tender. Drain the potatoes, and run them under cold water to remove the skin. Mash the sweet potatoes in a bowl, set aside and allow them to cool completely.
Preheat the oven to 350°F Line the bottom of a 9-inch round cake pan with parchment and spray the sides with nonstick spray. Place the 1/4-inch slices of the Cream Cheese Poundcake in the bottom of the pan.
Beat the cream cheese until fluffy, gradually adding the sugar until it is well blended. Add the eggs one at a time, beating well after each addition. Stir in the mashed sweet potatoes. Add the half and half, vanilla and nutmeg and mix well.
Pour the mixture into the prepared pan and bake for 1 hour or until the center is almost set. Remove from the oven and allow the cheesecake to cool. When the cake is cool, run a knife along the edges and remove it from the pan by inverting it onto a plate. Then transfer the cheesecake to a serving platter, crust-side down, and refrigerate until ready to serve.
Garnish with fresh berries.