Cebollas rellenas de bonito (Onions stuffed with bonito fish)

Hello everyone,

I thought today I would try a different kind of post. Last week I was travelling in Asturias in northern Spain (pictures and details still to come!) and I came across a dish that really piqued my interest. It was an interesting concept and so I decided to try them, especially as they were local. That dish is ‘Cebollas rellenas de bonito’.

What are cebollas rellenas?

The name of the dish is actually a description of what it is. ‘Cebollas’ are onions, ‘rellenas’ is an adjective meaning ‘filled’ and ‘bonito’ is a type of fish similar to tuna but smaller. Once all (the words) is said and done, you are left with bonito-stuffed onions (or cebollas rellenas de bonito), a delicacy of the region. But it isn’t just onions acting as a vessel for the bonito; the onions are covered with a light tomato-based sauce that pairs perfectly with the other flavours. Because of what an impact this dish had on me, I decided to look up some recipes online. Unfortunately for English speakers, I only found the recipes in Spanish, so I am looking to change that with this post. The following recipe is a somewhat modified version (including some improvements from my own experiences) from the HogarMania website‘s recipe of cebollas rellenas de bonito(original in Spanish). The result should be the featured image from this post (also from HogarMania).


  1. It has a relatively low prep time (approx. 20 minutes) but a large cooking time (3 hours minimum), so make sure you prepare the dish a few hours before you plan on serving it!
  2. The recipe has several variations but is always based on the slow cooking of the onions.
  3. Instead of cider, a splash of white wine of any variety including sweet ones may be used.
  4. You have to be very careful with the outer layer when emptying the insides of the onions as they break easily.

Ingredients (for 4 people):

  • 8 onions (medium)
  • 150 g of bonito (substitute: tuna) in olive oil
  • 250 mL (242 g) of diced tomatoes
  • 4 piquillo peppers (or other sweet, red pepper)
  • 1 boiled egg
  • 100 mL of dry cider (Asturian cider is typically dry)
  • 1 clove of garlic
  • extra virgin olive oil
  • 1 tbsp of flour
  • 1 bay leaf
  • salt to taste
  • parsley (chopped) to taste



To prepare the filling, chop up the bonito/tuna and place it in a bowl. Dice the boiled egg and 2 piquillo peppers (or other sweet, red pepper) and add them to the bowl. Add four large tbsp of diced tomato. Mix well.

The container (onions)

Peel and cut off the upper 1/4 of 8 onions and remove the centre of the onions, leaving several outer layers (easy to do with a scoop or small spoon). Take care to not break these outer layers as this creates a container for the filling. Cut or break the inner layers as necessary to remove them. You will use these to make the sauce.

Place the onions in a tray and add the filling to the hollowed-out onions.

Put a large amount of oil in a baking dish and slowly cook at a low temperature (Translator’s note: I used gas mark 3/165°C/325°F) until the onions are browned. Put them aside. (Translator’s note: WARNING: This step is likely to take a while and is dependent on the size of the onions that you use. Smaller onions will cook faster but have less filling. I had larger onions and this step took me over an hour. Although it is tempting to turn up the temperature, doing so may burn the onions rather than brown them.)

The sauce

To make the sauce, finely dice the leftover onion interiors and sauté them in a pan with a splash of oil. Stir in a tbsp of flour and sauté a bit more. Chop the other 2 piquillo peppers (or other sweet, red pepper) and add them along with the rest of the diced tomato, bay leaf, cider and 200 mL of water. Peel and dice the clove of garlic and grind it in a mortar. Add it to the pan along with a pinch of salt. Heat for a few minutes to combine flavours.

Pour the sauce into the baking dish with the stuffed onions, sprinkle chopped parsley on top, and cover and cook on low heat for approximately 2 hours. Dust with more chopped parsley and serve still warm.

And with that, you’re done! If you are wondering what you should do with the rest of the cider (assuming you haven’t been drinking it while cooking, which is how I usually do!), why not try drinking it as the pairing with the onions? Asturian cider usually comes in 750 mL bottles so there may be enough left for a glass for each person (depending on how much was used, of course).

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