Preheat your oven to 350°F (175°C) and grease a 12-cup muffin tin with non-stick cooking spray or melted butter.

In a blender, combine the melted unsalted butter, granulated sugar, room temperature eggs, whole milk, all-purpose flour, fresh lemon juice, lemon zest, vanilla extract, and salt. Blend until smooth.

Pour the batter evenly into the greased muffin cups, filling each about two-thirds full.

Bake for 28-32 minutes until the tops are golden brown and the centers jiggle.

Remove from the oven and let cool for 10 minutes. Run a knife around the edges to loosen them.

Transfer to a wire rack to cool completely, then chill in the refrigerator for at least 1 hour before serving.