Arequipe is Colombian dulce de leche made from scratch: fresh milk and sugar cooked down for about two hours until they caramelise into a thick brown cream. The baking soda is what gives it its colour and keeps the milk from curdling. Four ingredients, and constant stirring.
Stirring without stopping is the whole recipe: milk and sugar catch on the bottom as soon as they thicken, and one scorched patch ruins the batch. Arequipe tastes better once it has cooled completely. It is the same thing Argentina and Uruguay call dulce de leche.