To make the Peruvian-style pot roast: In a medium Dutch oven, set over medium heat, add the oil. When hot, add the onion and sear on first side for 1 to 2 minutes, until browned. Flip pieces of onion over and cook on opposite side for an additional minute or so. Remove the onion from the pot and set aside.
If needed add an additional tablespoon of olive oil. Sprinkle both sides of the chuck roast with salt and pepper. Turn the flame up to high heat and when the oil is hot, using tongs, place the chuck roast in the pot and brown on first side for about 5 minutes. Flip over and cook on the opposite side for an additional 5 minutes. Remove from the heat and preheat the oven to 300 degrees F.
Meanwhile, to a blender, add the cilantro, jalapeño, garlic, thyme, cumin, salt, coriander, paprika and 1/2 cup of beef broth (you can eyeball this measurement). Pulse until very smooth. Reserve about 1/4 of the cilantro mixture in a bowl (we’ll add this later). Pour the remaining 3/4 of the cilantro mixture into the pot with the beef broth and pour in the remaining 2 3/4 cup beef broth. Give the liquid a stir and place a cover on top. Mix in the reserved onion. Transfer to the oven to braise for 3 to 3 1/2 hours, until the meat is able to pull apart. Just before serving, skim fat off the top (if you like, I did because I don’t like that much fat). And then pour in the remaining cilantro mixture and mix.
To make the silky-smooth cauliflower puree: Bring a large pot of water to a boil. Drop in the cauliflower florets and cook until very tender, about 5 to 6 minutes. Drain and run the cauliflower under cold water. To a high-powered blender (such as a Vitamix), add the ghee and then top with the cauliflower. Pulse until mostly smooth, about 1 minute, stopping and scraping down the sides as needed. Pulse on high for about 2 minutes, until silky smooth, adding a teaspoon or two of ghee, if needed. Add salt and pepper to taste and blend once more until combined.
When the pot roast is ready, pour the cauliflower in a pot and warm over low heat. Divide between bowls and top with a piece of pot roast, a sprinkling of cilantro, green onion and a squeeze of lime.