Preheat the oven to 350F. Prepare 3 8-inch cake pans.

Zest the orange and juice the oranges. Separate the egg whites from the yolk.

Mix the flour, sugar, baking powder and salt together in a bowl.

Mix the egg yolk, orange juice, zest, and vegetable oil together.

Make a well in the center of the dry ingredients and add the wet ingredients.

Add the cream of tartar to the egg whites and mix to stiff peaks.

Pour the egg yolk and flour mixture to the meringue.

Mix with a balloon whisk until combined

Then use a spatula to finish mixing.

Mix the batter while you turn the bowl.

Pour the batter evenly into the three cake pans and bake for 25-30 minutes or until a toothpick comes out clean.

Mix the orange juice and zest with the powdered sugar. Add less orange juice if you want a thicker glaze. Add the glaze to the top of the cake.

Add sugar and water to a medium saucepan with a candy thermometer. You are heating this mixture to a softball stage 235°F.

In a mixing bowl add the egg whites (make sure the bowl is clean and dry). With the whisk attachment mix until the egg whites until it gets to stiff peak.

When the hot sugar heats to 240°F, turn the mixer on high and slowly pour the hot syrup to the egg whites.

Continue mixing until the bowl is cool to touch. Then add the butter one piece at a time. The mixture might look curdled at first, just keep on mixing. Mix until fully incorporated.

Add the orange zest lemon juice and orange juice to the buttercream and mix until combined.