Toss Romanesco and 1/2 of the carrots with olive oil and salt. Roast them on sheet tray at 350F for 15 minutes or until tender crisp. Reserve for later.
Place remaining carrots in a small pot with onions, olive oil and salt. Saute 5 minutes, then add water to the top of the carrots. Cook until carrots are soft. Blend carrot mixture in blender until puree forms. Season with salt.
Get saute pan hot on stovetop. Add canola oil until you see the first whisp of smoke. Season scallops with salt and add to hot pan, without crowding. Saute 1 minute. Flip scallops and cook 30 seconds.
Plate carrot puree on bottom of plate. Arrange blood orange segments along with sauteed scallops. Finish plate with roasted carrots and Romanesco.