Preheat oven to 325°F (160°C). Grease and flour a 10-inch tube pan.
In a medium bowl, whisk together the flour, baking soda, and salt. Set aside.
In a large bowl, cream together the softened butter and granulated sugar until light and fluffy.
Beat in the eggs one at a time, then stir in the vanilla extract.
Gradually add the dry ingredients to the wet ingredients, alternating with the milk, beginning and ending with the dry ingredients. Mix until just combined. Do not overmix.
Gently stir in the 7-Up soda.
Pour the batter into the prepared tube pan and spread evenly.
Bake for 60-75 minutes, or until a wooden skewer inserted into the center comes out clean.
Let the cake cool in the pan for 10-15 minutes before inverting it onto a wire rack to cool completely.
Notes
This cake is delicious on its own or served with a light glaze or fresh berries.