Marinate the pork loin with your favorite rub or just salt and pepper. Let rest for 1 hour or overnight.

Preheat oven to 350°F (175°C).

Roast the pork loin until it reaches an internal temperature of 145°F (63°C). Approximately 30 to 40 minutes, depending on your oven. Take care not to overcook.

Let the pork loin rest, then refrigerate to cool.

While the pork loin is cooking, prepare the sauce.

In a blender or food processor, combine tuna, capers, garlic, Cajun spice, lemon zest, and juice. Blend until smooth.

Add mayonnaise and blend again until fully incorporated.

Chill the sauce in the refrigerator until ready to use.

Thinly slice the red onions—using a mandoline will give the best results.

In a saucepan over medium heat, combine the vinegar, water, sugar, and salt. Stir until fully dissolved, about a minute.

Remove the mixture from heat and let it cool slightly before pouring over the sliced onions.

Allow the onions to sit at room temperature until completely cooled, then transfer them to the refrigerator.

The onions will be ready to use once they develop a vibrant pink hue and soften—this takes about an hour for very thin slices or overnight for thicker ones.

Store in the fridge and use within two weeks.

Drain and fry extra capers in oil until crispy. Set aside.

Slice the chilled pork loin as thin as possible; a meat slicer works best.

Arrange the sliced pork loin on a platter, fanning out the pieces.

Drizzle the Cajun tonnato sauce over the meat.

Garnish with fried capers, diced tomatoes, and pickled onions.

Enjoy!