For the cupcakes: Preheat oven to 350° F. Prepare 2 regular cupcake pans (24 cupcakes). Use paper cupcake liners or just spray the cupcake wells lightly with cooking spray.

In a large bowl, whisk together dry ingredients. With a spoon, make 3 large holes in the dry ingredients.

In a small bowl, combine vegetable oil and vinegar. Pour this into the 3 holes in the dry ingredients. Then pour the water over the entire mixture. Mix with a fork. Add vanilla and stir. Divide evenly into the 24 cupcake wells.

Bake for 25 to 30 minutes, removing from the oven as soon as a toothpick comes out clean. (This can also be made in a 9" x 13" cake pan - bake for 30 to 35 minutes, until toothpick comes out clean.)

For the caramel: Add the sugar to a small saucepan and pour the water over it. With the heat on low, swirl the pan around until the sugar has nearly dissolved. Be careful to not let it boil yet. If it starts getting too hot, remove it from the burner for a few seconds, while continuing to swirl. Once the sugar has mostly dissolved, raise the heat to medium-high and bring the mixture to a boil. Cover it immediately and let it boil for 2 minutes.

Uncover and continue swirling the mixture until it becomes dark amber. Be VERY careful here. You want it to be dark, but it can go from dark to burning in seconds. Once it goes from golden amber to dark amber, take it off the heat immediately.

Slowly pour the cream into the dark amber mixture, whisk continually. Be careful, as the caramel will start splattering if you pour too fast. Whisk until combined, then set aside. Let caramel cool to room temperature.

For the buttercream: Combine the egg whites, sugar, and cream of tartar in the stainless steel bowl of an electric stand mixer. Bring a large pan of water to simmer on the stove, making sure that when you place your mixer bowl into it, that the bottom of the bowl is sitting in the water just a bit. Set the mixer bowl in the pan of simmering water and whisk constantly until the mixture is extremely foamy and reaches 140° F on an instant-read thermometer. Be very careful to not let the egg whites curdle. If they start to curdle, they are getting too hot, too fast - remove the mixer bowl for a short while and reduce the heat a bit.

Move the bowl to the stand mixer and beat on high speed for 3-5 minutes, until the meringue mixture holds glossy, marshmallowy peaks. Remove the meringue to another bowl and place the empty mixer bowl back on the stand mixer. Then add half the butter and one-third of the meringue to the mixer bowl and beat until well combined. Continue to add the remaining two-thirds of the meringue a dollop at a time. The mixture may look curdled at this point, which is a bit alarming after going through all this work, but adding the remaining butter a tablespoon at a time will smooth things out. It really does come together at the end.

With the mixer on low, add the room-temperature caramel and mix until evenly combined. Do NOT add warm/hot caramel, as it will melt the butter!!

To finish: With a pastry bag and tip, swirl the caramel buttercream on top of individual cupcakes - this buttercream recipe makes enough to add a large mound of frosting to 24 cupcakes. Drizzle on your favorite caramel sauce, and then sprinkle with sea salt flakes to finish them off.