To make a cake in the shape of a number 7, start by preparing your cake batter according to the recipe of your choice. Pour the batter into two separate pans - one shaped like a number 7 and another round or rectangular pan. Bake both pans according to the recipe's instructions. Once the cakes are fully baked and cooled, carefully remove them from the pans. Place the number 7-shaped cake on your serving platter and frost it with your desired frosting. Next, take the round or rectangular cake and cut out a section that resembles the top part of the number 7 silhouette. Transfer this cutout piece onto the frosted number 7 cake, aligning it to complete the shape. Frost this piece as well and decorate it further if desired.