Preheat the oven to 425°F (220°C). Line a muffin tin with paper liners.
Melt 1/2 cup salted butter in a microwave-safe bowl on 50% power in 20-second increments until fully melted.
In a large bowl, use a hand mixer to beat the melted butter and 3/4 cup granulated sugar until well combined, about 1 minute. Add 2 large eggs and 1 teaspoon vanilla extract, then mix until just incorporated.
Add in 3.4 ounce package pistachio instant pudding mix, 2 teaspoons baking powder, 1/2 teaspoon salt, and 1/2 cup milk. Mix to combine. Add in 2 cups all-purpose flourr and mix until flour has been incorporated. The batter will be thick.
Divide the batter evenly among the muffin cups, filling each about ¾ full. Sprinkle the tops with 1/4 cup granulated sugar.
Bake for 7 minutes at 425°F (220°C). Without opening the oven, reduce the temperature to 350°F (175°C) and continue baking for 10 more minutes, or until a toothpick inserted in the center comes out clean.
Remove from the muffin tin and transfer to a wire rack to cool completely.