Preheat oven to 325 degrees. In the bowl of an electric mixer fitted with the paddle attachment, cream together butter and sugar. Add eggs one at a time, mixing after each addition. Combine flour and salt, then add it 1 cup at a time, mixing after each addition. With the mixer on low, slowly add the 7-Up until combined. Add 1 tablespoon of both lemon and lime zest and mix. Scrape the bowl and mix again.

Thoroughly spray a bundt pan with nonstick baking spray. Add large spoonfuls of batter until the pan is filled, then even out the surface. Bake for 1 hour 10 to 1 hour 15 minutes. Remove the pan from the oven and let it sit in the pan for 15 minutes. Carefully turn it out onto a cake plate and let it cool.

Combine all the glaze ingredients in a bowl and gently whisk until thick but pourable. Use a large spoon to drizzle it all over the cake. Let the glaze set, then slice and serve! Optional: Sprinkle with a little extra lemon and lime zest.