Prepare the Scallops: Pat the scallops dry with a paper towel and season both sides with salt and pepper. Heat a cast-iron skillet over medium-high heat and add the grapeseed oil. Once the oil is shimmering, sear the scallops for 2-3 minutes on one side until golden brown, then flip and cook for an additional 1-2 minutes. Remove from the pan and set aside.
Make the Saffron Risotto: In a medium saucepan, heat the broth and add the saffron threads to steep. In a separate pan, sauté the onion or shallot in butter until softened. Add the Arborio rice and toast for 1-2 minutes. Gradually add the warm saffron broth, one ladleful at a time, stirring constantly until the rice is creamy and al dente. Stir in Parmesan cheese and adjust seasoning as needed.
Make the Lemon Butter Sauce: In a small saucepan, melt the butter over low heat. Gradually whisk in the lemon juice and season with salt and pepper. Add fresh herbs if desired.
Plate the Dish: Spoon the saffron risotto onto the center of the plate, arrange the scallops on top, and drizzle with lemon butter sauce. Garnish with fresh herbs.