Step 1

Preheat the oven to 325˚F. Spray a jelly roll pan (10x15 inches) with nonstick baking spray. Rub with a small piece of paper toweling to coat the bottom and sides of the pan. Set aside. (You can also use a half sheet pan (13x18 inches) but the cake will not be as thick (tall).

Step 2

Combine the oil and butter in a microwave-safe bowl or measuring cup. Microwave on high power for 30-40 seconds or until the butter is melted.

Step 3

In a medium-large bowl, combine the two sugars with the butter/oil mixture. Whisk to combine. The mixture will look a little sandy at this point.

Step 4

Add the two eggs and whisk vigorously for 30 seconds. The mixture should look nice and smooth now.

Step 5

Add the baking powder, baking soda and salt. Whisk again until incorporated then add the buttermilk and vanilla and whisk to combine.

Step 6

Add the flour and stir just until incorporated.

Step 7

Switch to a silicone spatula or wooden spoon now. Add the zucchini and stir until well distributed.

Step 8

Pour the batter out onto the prepared pan and spread to an even layer.

Step 9

Bake for 23-25 minutes or until the center of the cake feels firm when lightly touched. You can also use an instant thermometer to determine doneness. It should read 200-205˚F (93-96˚C). If you make this cake in a half-sheet pan, it will take a little less time to bake.

Step 10

For the butterscotch buttercream:

Step 11

While the cake is cooling, make the icing by melting the butter in a medium-large saucepan over medium heat.

Step 12

Add the brown sugar and whisk vigorously until the mixture is smooth and bubbling. At first the butter and sugar will seem separate but will come together with whisking.

Step 13

Add the half and half (or cream) and the vanilla extract. Whisk until nice and smooth.

Step 14

Turn off the heat to very low leave the pot on the burner.

Step 15

Add the powdered sugar, 1 cup at a time, whisking until smooth between each cup. You should have a smooth but nicely spreadable consistency. I like to make it a little thinner than I think I want as it will thicked a bit, the minute you start spread it out onto the cake. If it’s still a little thick, add a bit more half-and-half (or cream).

Step 16

Spread the icing over the warm cake. Use a small silicone spatula or the back of a spoon to make decorative swirls, if desired. Sprinkle with a bit of flaky sea salt, if desired. Wait for the cake to cool (if you can) then serve and enjoy!

Step 17

This cake keeps well for several days covered with foil or plastic wrap. Just make sure the cake is completely cool before covering.

Step 18

This cake also freezes well. I like to cut it into serving-size portions and wrap each one with plastic wrap. Then it’s easy to pull a few out when the sweet tooth strikes or a friend stops by for a cup of coffee.