To Make the Batter:

1. Preheat oven to 325°F.  An oven thermometer will help you determine where you need to set your oven in order to get to a true 325°F.
2. Sift the flour and kosher salt into a medium bowl.  Set aside.
3. Place the room temperature butter in a large mixing bowl or the bowl of your stand mixer.  Mix on low speed until smooth. 
4. Slowly add the granulated sugar and mix on medium speed until the mixture is light and fluffy.  Scrape as needed to ensure even mixing. Also, don’t skimp on this step! If you’re unsure about what properly creamed butter and sugar look like, check out this tutorial on How to Cream Butter and Sugar from the BwB blog!
5. Add eggs, one at a time, mixing until each addition is fully incorporated.  Scrape the sides and bottom of the bowl as needed.  This step is especially important for cake rise in this particular cake, as there is no chemical leavening. 
6. Add vanilla extract, lemon extract, and lime extract and mix until thoroughly combined.
7. Add half of the flour mixture and mix on low speed until combined. I sift my flour/salt mixture directly into the batter for a last extra oomph, but you don’t have to do this.
8. Measure the 7-Up just before adding, in order to maximize the bubbles. It’s important to weigh your 7-Up, since you don’t want to be fooled by the volume of the bubbles!
9. With the mixer on the lowest speed, add all of the 7-Up and mix until just combined.  Don’t add too quickly or the carbonation will bubble over! 
10. Add the second half of the flour mixture and mix on low speed until combined.  Stop mixing just as soon as the mixture is fully together. 
11. Using a rubber spatula, fully scrape the sides and bottom of the mixing bowl.  Then, mix the batter until it is smooth and consistent.  Make sure to fully scrape the bottom of the bowl!
12. Grease a 10-12 cup bundt pan with the remaining butter and flour and place the batter in the pan.

To Bake the Cake:

1. Bake the cake at a true 325°F for 60-70 minutes, or until an instant read thermometer reads 210°F-215°F in the center.  Alternately, the cake is done with a toothpick inserted into the center comes out clean and a fingerprint indentation bounces back.
2. Allow the cake to remain in its pan for 5-10 minutes, then invert onto a cooling rack to cool completely.

To Make the Lemon Simple Syrup:

1. Combine sugar, water, and salt in a small saucepan and bring to a boil.  Stir occasionally until the solids are completely dissolved.  Remove from the heat, and add the lemon juice and pure vanilla extract.
2. Allow the simple syrup to cool completely, then use a pastry brush to brush the simple syrup over the cooled cake.

To Make the Final Glaze:

1. Combine the confectioner’s sugar, fine sea salt, and 3 tablespoons of the 7-Up in a large bowl.
2. Mix with a whisk or a spoon until completely smooth. Add 7-Up soda, one teaspoon at a time, if necessary. Make sure to allow the existing 7-Up to moisten the confectioner’s sugar before adding any additional liquid.
3. Completed glaze should be just pourable and should have the consistency of thick honey.
4. Using a spouted measuring cup, spoon, or squeeze bottle, drizzle final glaze over the cake. 

To Store:

This cake can be stored on a countertop for up to five days.