recepto

Both senses are real, and PIV lists them both. Recepto is the doctor's prescription and the cook's recipe, in that historical order. That is not sloppiness in Esperanto: it is exactly what happened in English too, where recipe and receipt are the same Latin word and a Victorian cookbook prints receipts for cakes. The two uses share one idea, a written set of instructions for making something up, and Esperanto simply never split them.

Context does the disambiguating, and it always can. Recepto por pano is a recipe. Recepto de la kuracisto is a prescription. If you need to be unmistakable, kuirrecepto narrows it to cooking and kuracila recepto to medicine, but both are heavier than the situation usually requires.

Why the Latin imperative matters. A prescription used to open with Recipe, meaning "take", addressed to the pharmacist: take so much of this, so much of that. The instruction became the name of the document. The R with a stroke through its leg still printed at the top of prescription pads is that same word.

Around it. Instrukcio is instructions in general, preskribi is to prescribe, and preskribo is the prescribing rather than the paper. Kuiri is to cook and kuirlibro is the cookbook the recipes live in.