Preheat oven to 325°. Grease and flour a mini loaf pan (approximately 5 ¾ x 3 ¼ inches). You can buy disposable ones at the grocery store or invest in good ones. (Tip: when buying a mini loaf pan, buy 3. One regular loaf = 3 mini loaves. Lately I’ve seen a large pan that has 3 mini loaf pans in it like a cupcake tin. This would be much easier to use than 3 little pans.)
Mix flour, baking powder, and salt in a small bowl. Whisk well and set aside.
Cream butter in a large bowl with hand-held mixer for 1 minute. Add the sugar and beat on medium speed until fluffy, about 2 minutes. Add the egg and egg white separately, mixing well in between each addition. Scrape down the sides of the bowl as needed. Beat in the lemon zest and vanilla and mix until combined.
Add 1 tablespoon of the milk or heavy cream and half of the flour mixture to your batter. Mix on medium speed until just combined. Repeat with the rest of the milk and flour mixture. Beat until just combined. Scrape the sides and stir into batter.
Pour into mini loaf pan. If your loaf pan is a loose pan (not joined with two others as a muffin tin is), place it on a baking sheet before placing in the center of your oven. Bake for about 25-30 minutes, until a toothpick comes out clean. Let cool completely before removing from pan.
To make the Faux Grilled Cheese: Mix your favorite white icing with food coloring to turn it light orange (the color of cheddar or American cheese). Cut two slices of your mini loaf and make a sandwich with the orange tinted icing. Use a brown food writer to draw lines on the sides to simulate grill marks.
To serve as a dessert for two: Slice and serve with whipped cream or ice cream and fresh berries. Or, make a simple glaze to drizzle on the top. Lemon Glaze: 1/3 cup powdered sugar, 4 teaspoons heavy cream or milk, 1/8 teaspoon lemon juice and 1/8 teaspoon lemon zest. Mix together and pour over cake. To make a Vanilla Glaze, omit lemon zest and replace 1/8 teaspoon vanilla extract for the lemon juice.