Step 1

Preheat oven to 200 Celcius (400 Fahrenheit). Line a 9" round cake pan or an 8" square cake pan with parchment paper. Set aside.

Step 2

First, make batter A. In a mixing bowl, cream butter, sweetened condensed milk, and rum at medium speed until fluffy, about 8 minutes. Add in cake flour, spekkoek seasoning, and salt. Mix again until well combined. Set aside.

Step 3

Next, make batter B. In another mixing bowl, whisk egg yolks and sugar at high speed until thick.

Step 4

Next, make batter C. In another mixing bowl (stainless steel is best for this), whisk egg whites until foamy, then add cream of tartar, and sugar in 3 batches. Continue whisking until stiff peak.

Step 5

Now we will need to combine all the different batters together. First, add batter B into batter A, mix until well combined. Then using a spatula, fold in 1/3 of batter C into batter A/B combo until well mixed, then fold in the rest of batter C until well mixed.

Step 6

For the first layer, spread a small amount of batter, about 1/8 inch, on the prepared pan. Bake in the center rack of preheated oven until golden brown, about 8 minutes.

Step 7

For the second layer onward, turn off the oven, but switch on the oven broiler, position the rack near the top closer to the heating element. Spread batter evenly (about 1/8 inch), the batter will look more melted and runnier once placed into the pan, and bang the pan on the countertop to remove air bubbles. Broil for 1-2 minutes until golden brown, you will need to stand watch and be extra careful from here on out. Each broiler heats differently, and yours may need less or more time, but be extra diligent in the first few layers so you don't accidentally end up with burnt cake. Once a layer is cooked and looks golden brown, add another layer, bang it a bit on the countertop, and broil again. Continue doing this until the batter is all used up.

Step 8

Cool the cake in the pan for 30 minutes. Then gently work a sharp knife around the edges to loosen the cake. Gently turn the cake out onto a wiring rack, and cool the cake completely.