Adjust rack to top position and preheat oven to 425 degrees. Wash and dry produce.

Dice potatoes into ½-inch pieces. Toss on a baking sheet with a large drizzle of oil, oregano, salt, and pepper. Roast on top rack until browned and tender, 20-25 minutes.

Meanwhile, halve, peel, and cut half the onion (whole onion for 4 servings) into ½-inch wedges. 

While potatoes roast, in a small pot, combine rice, 1¼ cups water (2¼ cups for 4 servings), and a pinch of salt. Bring to a boil, then cover and reduce to a low simmer. Cook until rice is tender, 15-18 minutes.

Keep covered off heat until ready to serve.

Meanwhile, in a small bowl, combine chimichurri and mayonnaise.

Heat a drizzle of oil in a large pan over medium heat. Add onion wedges; cook, stirring occasionally, until lightly browned and slightly tender, 4-6 minutes. Add tomato paste and cook until brick red in color, 30-60 seconds. 

Add turkey* and cook, breaking up meat into pieces, until cooked through, 3-4 minutes.

Fluff rice with a fork; stir in 1 TBSP butter (2 TBSP for 4 servings).

Divide rice and potatoes between plates in separate sections. Top potatoes with lomo saltado. Drizzle with chimichurri mayo and as much Sriracha as you like. Serve.