Preheat oven to 350°F. Line a standard muffin tin with cupcake liners.
In a mixing bowl, whisk together the flour, baking powder, ½ teaspoon salt, and baking soda.
In the bowl of an electric mixer, preferably fitted with the paddle attachment, beat ½ cup butter with the sugar on medium-high speed for 5 minutes. Scape down the sides of the bowl as needed.
Add the eggs, one at a time, beating well and scraping down the sides of the bowl after each addition. Beat in 1 tablespoon vanilla. Scrape down the sides of the bowl.
Turn down the mixer to medium, add ¹/₃ of the flour mixture, then half the buttermilk, another third of the flour mixture, the rest of the buttermilk, and finally, the rest of the flour. Add enough food coloring to get a vibrant green. Give the batter a final mix by hand with a spatula.
Divide the batter evenly among the prepared muffin tins (an ice cream scoop works well for this). Bake for 18–20 minutes or until a toothpick inserted into the center comes out clean. Let cool in the pan for 10 minutes then remove to a wire rack to finish cooling.
For the frosting, cream together the remining ½ cup butter, ¼ teaspoon salt, and cream cheese. Beat on medium-high speed until creamy. Beat in 1 teaspoon vanilla. Turn the mixer to low and gradually add the powdered sugar. Beat until completely combined.
Frost the cooled cupcakes generously and decorate with sprinkles.