What spices go with quinoa
Quick answer
Cumin, Ají amarillo, Huacatay — in roughly that order of how well established each combination is.
Each is explained below, with the cuisines it belongs to and the point at which it stops working.
Why quinoa behaves as it does
Quinoa carries saponins in its coating, which are bitter and are the reason it is rinsed before cooking — an unrinsed batch tastes soapy and no spicing corrects it. Once rinsed it is mild with a faint grassiness, and it behaves like a neutral grain that browns well: toasting the dry seed before cooking develops a nuttiness that gives spices something to sit on. Its Andean home cuisine seasons it with ají amarillo, huacatay and cumin, which is worth knowing because almost nothing written about quinoa in English reflects it.
Strong
Cumin
StrongThe Andean pairing, and largely absent from the English-language writing about quinoa. Cumin's earthiness meets a grain that is mild and faintly grassy, and toasting the dry seed first develops a nuttiness that gives it something to sit on.
How: Toasted with the dry grain before cooking
Ají amarillo
StrongQuinoa is Andean and so is ají amarillo, and the combination is what quinoa tastes like in the place it comes from. Fruity moderate heat against a mild grain, usually as a paste stirred through rather than a powder.
How: Stirred through as a paste; In a Peruvian quinoa stew
Good
Huacatay
GoodThe other half of the Andean answer. Huacatay is resinous and minty at once and it gives quinoa an aroma the grain has no way of supplying itself.
How: Blended into a sauce served with quinoa
Cuts and forms
White, Red, Black, Puffed. These do not all take the same spicing — the notes above flag where the difference matters.