Preheat oven to 350 degrees F. Thoroughly grease a 12-cup muffin pan. In a bowl, beat butter and sugar until well-combined; add eggs and mix thoroughly. Stir in buttermilk. Into a large bowl sift flour, baking powder, baking soda and salt; make a well in center. Pour buttermilk mixture into well and use a rubber spatula to blend with quick strokes. Do not overmix batter; it should still be slightly lumpy. Spoon batter into muffin tins, filling them three-quarters full, and bake until slightly puffed and golden, 18 to 20 minutes.
Yield: 12 muffins
Variations, add 1/2 cup of one of following ingredients: rinsed fresh blueberries; raisins or currants; chopped apples tossed with 1/2 teaspoon cinnamon; or poppy seeds tossed with 2 teaspoons lemon zest or 3 drops lemon oil.