This spicy recipe for tuna ceviche makes a good taco filling. Consider serving with sliced radish and small tortillas.
(Adapted from Mark Bittman, Two Hot Tamales, Wikipedia’s ceviche article, etc.)
1 lb fresh raw tuna
1/2 small red onion
1 clove garlic
4 limes, juiced
1/2 bunch fresh cilantro
1/2 fresh jalapeno with some seeds removed or 1 serrano pepper
kosher salt
Dice onion, garlic, and jalapeno. Chop tuna into 1/4 - 1/2 inch cubes. Toss tuna, garlic, jalapeno, and tuna with lime juice. Let stand 15 minutes.
Add cilantro and salt to taste.
Be careful not to over-spice! We made this a bit heavy on the pepper first time around.