Meyer Lemon Upside-Down Cake — Les Petites Gourmettes

Ingredients

• 1 ½ sticks unsalted butter, room temperature and divided
• 3/4 cup plus 2 tablespoons light brown sugar
• 2 Meyer lemons, sliced paper-thin crosswise, seeds discarded
• 1 ½ cups flour
• 2 teaspoons baking powder
• 1/4 teaspoon salt
• 1 cup sugar
• 1 teaspoon vanilla extract
• 2 large eggs, separated
• 3/4 cup milk
• 1/4 teaspoon cream of tartar