Preheat the oven to 350°F. Grease two 9-inch round cake pans and set aside. In a stand mixer, cream together butter and sugar. Add the vanilla and eggs, mixing on low speed until just combined.
In a medium bowl, whisk together gluten free flour, baking powder, baking soda, and salt. Sift the flour into the butter mixture, mixing on medium-low speed.
Add the sour cream, lemon juice, lemon zest, and half and half, mixing on medium-low speed until just combined. Pour evenly into the two cake pans.
Bake for 30-35 minutes, or until a toothpick comes out clean. Let cool completely before decorating.
For the Frosting
Add cream cheese, powdered sugar, and vanilla to the stand mixer. Cream everything together on medium-low speed until just combined. Be careful not to over-mix.
Using the whisk attachment on medium-high speed, very slowly add the cream down the side of the mixing bowl. After the cream is completely added, set the mixer on high speed for about 2-3 minutes.
Once the frosting begins to form stiff peaks, stop the mixer and scrape the sides and bottom of the bowl. Start the mixer again until the whipped cream is fully formed, then add the lemon juice and lemon zest. Mix on low until just combined, then store in the refrigerator until ready to use.
Notes
Click on the time in the instructions to start a timer!StorageRefrigerate for 3-4 days in an airtight container. Because the frosting is dairy-based, this cake has to be refrigerated. Freeze for up to 1 month. Place the entire cake in the freezer for about an hour, then wrap the cake in plastic wrap and aluminum foil and place back into the freezer. Freezing the frosting first prevents it from getting messed up when wrapping. Cooking Tips
If you want to make a crumb coat, just use a thin layer of frosting and refrigerate the cake for 30 minutes until it dries. You should be able to see crumbs in this layer. After it's dry, you can decorate normally with a decorative layer on top.
If you use a stand mixer for the cake batter, use a paddle attachment. For the frosting, use the whisk attachment.
If you don't have a stand mixer, you can also make this using an electric hand mixer.
Let the cake come to room temperature before serving (but don't leave it out for too long, the frosting is still dairy!) If it's too cold, it will have the texture of a really dense cake.