1 ½ cups (3 sticks) Unsalted Butter: This is the absolute backbone of your cake. It must be a high-quality butter, and crucially, it must be at true room temperature (around 65°F to 68°F). It should yield slightly to a gentle press but not look greasy or melted. Substitution: If you only have salted butter, omit the additional salt in the recipe.3 cups Granulated Sugar: The sugar does more than just sweeten; its sharp crystals physically punch microscopic air pockets into the butter during the creaming process. This provides the primary leavening for the cake. Substitution: For a slight caramel note, swap half a cup of granulated sugar for packed light brown sugar.5 Large Eggs: Eggs act as the binder and provide additional liquid and fat. They absolutely must be at room temperature to prevent the butter emulsion from breaking.3 cups All-Purpose Flour: A medium-protein flour provides the necessary structure to support the heavy butter and sugar without becoming tough. Substitution: For a slightly tighter crumb, you can use cake flour, but standard all-purpose yields the most traditional texture.½ cup Whole Milk or Buttermilk: Adds essential moisture and helps tenderize the gluten. Substitution: Full-fat sour cream or plain Greek yogurt will add a wonderful tang and incredible moisture.1 tablespoon Pure Vanilla Extract: Because there are so few ingredients, high-quality vanilla extract is essential for a rich, aromatic flavor profile.½ teaspoon Fine Sea Salt: Enhances all the inherent flavors, balancing the intense sweetness and highlighting the buttery notes.