Red velvet layer cake with natural coloring and cream cheese ermine frosting

For the cabbage dye, boil red cabbage in water until the color leaches out, then add a little red wine vinegar to turn it hot pink.

Put half a cup of annatto seed and a cup of neutral oil in a saucepan and heat on medium a couple of minutes, until the seeds sizzle. Take off the heat and cool completely to room temperature.

Heat the oven to 350. Coat three eight-inch cake pans with room temperature butter and line with parchment, smoothing out air bubbles.

Whisk the cake flour, salt, baking powder, baking soda, granulated sugar and natural cocoa powder together; sift the cocoa if it is lumpy.

Strain the annatto oil. Mix it with the cabbage dye, then whisk in the sour cream.

Whisk the four eggs separately until streak-free.

Add about half the liquid ingredients to the dry and mix until all the flour is coated, then add the rest of the liquid, then the eggs, and mix until evenly combined.

Divide the batter between the pans, about 450 grams each, weighing to even them.

Bake on the upper and lower thirds of the 350 oven for 20 to 25 minutes, rotating after 15, until springy to the touch and pulling from the sides. Cool in the pans.

For the frosting, whisk five tablespoons of flour into the milk off the heat until there are no lumps, then cook in a small saucepan, whisking constantly, a couple of minutes until it thickens to a paste. Press through a sieve if lumpy.

Transfer to a bowl, press plastic onto the surface so no skin forms, and cool completely.

Add the sugar and salt and beat with a hand mixer until the sugar dissolves and no grit remains.

With the mixer at medium high, beat in the very soft butter one piece at a time, then the cream cheese, then a couple of teaspoons of vanilla, until thick, light and fluffy.

variation: the intended method creams the butter, cream cheese and sugar first in a separate bowl, then adds the cooled roux a tablespoon at a time, for a more stable emulsion.

Loosen the cooled layers around the sides, unmold, peel off the parchment, and level the inner two thirds of each dome with a serrated knife held parallel to the board.

Stack with a not-too-thick dollop of frosting between layers, the top layer upside down so the flat side is up; chill the frosting if it is too loose to hold its shape.

Apply a thin crumb coat over the top and sides and chill a couple of minutes to harden it.

Deposit the rest of the frosting on top, let it cascade down, and work it around the sides to the bottom.

Chill a few minutes for a cleaner slice, then cut.