How to Make It
In a medium cast-iron skillet, cook the bacon over moderate heat, stirring occasionally, until crisp, 6 to 7 minutes. Using a slotted spoon, transfer the bacon to a plate. Pour off all but 2 tablespoons of the bacon fat. Add the onion to the skillet and cook over moderately low heat, stirring occasionally, until soft and golden, about 25 minutes. Add the sugar and cook until the sugar is dissolved and the onions are glazed, about 2 minutes. Return the bacon to the skillet; season with cayenne pepper, salt and black pepper. Keep the bacon marmalade warm.
In a medium saucepan of salted boiling water, cook the carrots until tender, 5 to 7 minutes. Drain well. In a food processor, combine the carrots with the butter and harissa and puree until smooth. Add the cream and pulse until incorporated. Season with salt and black pepper. Scrape the carrot-harissa puree into the saucepan; keep warm over very low heat.
Season the scallops with salt and black pepper. In a large skillet, heat the olive oil until shimmering. Add the scallops and cook over moderately high heat until browned on the bottom, about 2 minutes. Turn the scallops and cook until just opaque throughout, about 1 minute longer. Transfer the scallops to plates and top with the bacon marmalade. Serve the carrot-harissa puree alongside.
Harissa is a North African chile paste. It is available in jars and tubes at specialty food shops.