Grease and lightly flour an 8-inch square baking pan. Whisk the flour, baking powder, baking soda, nutmeg and salt in a medium bowl. Beat ¾ cup sugar, oil, 1 teaspoon lemon peel and lemon juice in a large bowl at medium speed for 1 minute.
Beat in the egg at low speed until blended. Beat in 1/2 cup sour cream and milk. Slowly beat in the flour mixture until combined and spoon into the baking pan
Bake for 25 to 35 minutes or until golden brown and a toothpick inserted in the center comes out clean. Cool in the pan on a wire rack for 5 minutes. Invert the cake onto the wire rack and cool completely
Meanwhile, beat the whipping cream at high speed until slightly thickened. Add 3/4 cup sour cream, 3 tablespoons sugar and 2 teaspoons lemon peel and beat until soft peaks form.
Using a 2 1/4-inch round cookie cutter, cut the cake into 8 rounds. Slice each cake round horizontally in half to form two rounds.
To assemble the cake jars, place one round in the bottom of an 8-ounce (1/2 pint) mason jar. Top with a spoonful of the berries and cream.
Layer with second cake round and top with more berries and cream. Repeat for the remaining servings. Cover and store in the refrigerator.