Watch the video to see how to fold your own Twinkie molds out of aluminum foil if you don't have a canoe pan (cupcake pan will also work, though it doesn't give the right shape obviously)
Grease your pans well and set aside. (Cupcake pans do not use liners, just grease.)
Set oven to 375ºF.
In a large mixing bowl, beat the egg yolks on medium speed until loosened up, 30-60 seconds.
Gradually add in the sugar. Once sugar is all in, increase the speed to medium-high and beat for 3 minutes. The mixture will be light and creamy-looking and will have almost doubled in volume.
Reduce speed to low and slowly pour in boiling water, careful not to splash yourself, then vanilla and lemon juice. Make sure it's well combined.
Whisk the flour, baking powder and salt together in a small bowl and add it gradually in to the egg mixture, still on low speed, until you have a smooth, creamy batter. Set aside.
In a very clean bowl, beat the reserved 3 egg whites and cream of tartar for 30-90 seconds on high heat with a whisk attachment until soft peak form. The whites should be foamy and somewhat stiff, though still moist and soft looking.
Fold in one quarter of the whites into the first batter.
Gently fold in the remaining whites.
Divide batter between 12 molds and bake 13-15 minutes, until the edges have begun to pull away from the sides and the tops are set. Cool on racks in the molds.
Make the filling while the cakes cool: Beat butter, vanilla, and cream together then slowly add in powdered sugar on low speed until combined. Beat on medium speed for 30-60 seconds until smooth. Put into a ziploc bag or piping bag and leave at room temperature.
Once the cakes are cool, unwrap from their molds. Use a chopstick to poke 3 holes down the center of each cake, lengthwise, being careful not to go all the way through the cake.
Cut a 1/4" tip off the corner of the icing bag and squirt a little icing into each hole, slowly and gently.
Serve the cakes the same day or the next day.
Recipe by Hilah Cooking at http://hilahcooking.com/homemade-twinkie-recipe/