Prepare a 9x13 inch baking dish with cooking spray.

Beat 4 large eggs in a bowl. Melt 8 tablespoons butter, 6 tablespoons lemon juice, zest of 2 lemons, and 1 cup sugar in a heatproof bowl over simmering water for 4-5 minutes. Whisk in eggs and cook for 20 minutes until thickened. Chill the lemon curd.

In a pot, melt 4 tablespoons butter. Melt a 10-ounce package of marshmallows in the butter, then stir in 1 package of instant lemon pudding and fold in 6 cups Rice Krispies. Press into the prepared dish and cool.

Spread the chilled lemon curd over the cooled Rice Krispies base.

Whisk 2 egg whites, ½ cup sugar, cream of tartar, and sea salt in a bowl over simmering water for 6 minutes. Beat until stiff peaks form and mix in ½ teaspoon vanilla extract.

Spread meringue over lemon curd and toast under the broiler for 1 minute until golden. Cool and cut into squares.