Buck's Best Lemon Blueberry Cake

 Ingredients:

• 1 (15.25-oz.) box vanilla cake. Make sure you get the ingredients listed on the back of the box. 

• Juice and zest of 1 ½ lemons. Divide the juice and the zest.

• 1 ¾ cups of fresh blueberries.

• 3 tbsp. all-purpose flour.

• 2 sticks of softened butter.

• 3 cups of powdered sugar

• 1/4 cup heavy cream

• 1 tsp. pure vanilla extract

• Pinch kosher salt

• Thin lemon slices, for topping (optional)

Recipe:

1. Preheat the oven to 350º. Grease three 9" cake pans with cooking spray and line with parchment. Prepare cake mix according to package directions, then stir in juice and zest of 1 lemon.
2.  In a small bowl, toss 1 cup blueberries and flour until completely coated. Gently fold blueberries into the batter.
3. Divide cake batter evenly among prepared cake pans and bake until a toothpick comes out clean, 18 to 20 minutes.
4. Let cool in pans for 10 minutes, then invert onto a wire rack and let cool completely.
5. Make frosting: In a large bowl using a hand mixer or the bowl of a stand mixer using the whisk attachment, beat butter and 2 1/2 cups powdered sugar. Add remaining lemon juice and zest and heavy cream and beat until combined, then beat in vanilla and salt. (Add remaining 1/2 cup powdered sugar as desired for texture and flavor.)
6. Place a dab of frosting on cake plate to keep cake from moving and place a parchment strip on each side of the cake plate. Place down first cake layer and top with frosting, then repeat with the second and third cake layers and remaining frosting. Smooth frosting over the top and sides of your cake.
7. Garnish with remaining blueberries, lemon slices, and zest before serving.

Tips:

Can I use frozen blueberries?
Yes! They definitely won't look as pretty as the finishing garnish, but they'll do just fine in the batter. We toss our fresh berries with flour to keep them from sinking to the bottom of the cake, so be sure you are doing the same with your frozen ones too!

Should I use salted or unsalted butter?
For baking purposes, we always use unsalted butter. This way, you have full control over how much salt you add!

How long can this cake be kept at room temperature?
Frosted (but not yet cut into), this cake can last about 4 days at room temperature. Be sure to cover it with a bowl or glass cake cover to prevent dust/air/anything that might be floating around in your kitchen from landing on it, and to prevent it from drying out.

How do I keep the cake fresh once I've cut it?
You've got two options. One, cover all cut areas with plastic wrap to tightly seal in the moisture. Two, if you've got any leftover frosting, you can frost over the cut sides of the cake. Not only will this prevent the cake from drying out, the lucky recipient of the next slice will be rewarded with extra frosting!

I'm not a fan of buttercream, what other type of frosting would be good on this cake? 
We hear ya! Sometimes buttercream can be a little too rich. This cream cheese frosting recipe is one of our favorites. The tang of the cream cheese plays super well with the sweet berries.

How far in advance can I make this cake?
You can make the cake up to a week in advance! When it has cooled, wrap tightly in plastic wrap and store at room temperature. As for the buttercream, it can be made up to two weeks in advance in an airtight container in the refrigerator. Just give it a quick whip with your hand mixer to make it spreadable, and you're good to go!

Source: Lindsey Funston: www.delish.com/cooking/a52625/lemon-blueberry-cake-recipe