Preheat oven to 325 degrees Fahrenheit.
In a large mixing bowl, combine oil, eggs, whole milk, lime zest, and lime juice. Beat for 2 minutes until creamy.
In another large bowl, mix sugar, flour, baking powder, baking soda, and salt. Fold into the egg mixture until combined.
Grease two 9-inch or three 8-inch cake pans with nonstick cooking spray. Divide batter evenly into pans.
Bake three 8-inch cakes for 20-26 minutes or until a toothpick comes out clean. Bake two 9-inch cakes for 30-36 minutes. Let cool.
To make Lime Cream Cheese Frosting: In a large bowl, beat together softened butter and cream cheese for 4-5 minutes until fluffy. Add powdered sugar, lime juice, and lime zest. Beat until smooth. Chill.
Remove cakes from pans. Spread frosting on top of one cooled cake layer. Place the other cake layer on top and spread frosting all over. Garnish with fresh lime slices. Enjoy!