Prep the seafood: Pat shrimp and scallops dry. Season lightly with salt and pepper.
Dry seafood sears better and won’t steam.
Cook the zucchini noodles: Heat a large skillet over medium. Add a drizzle of olive oil, then the zoodles with a pinch of salt. Toss 2–3 minutes until just softened.
Transfer to a colander to drain excess moisture. If using shirataki, rinse well, boil 2 minutes, drain, and dry-sauté 2 minutes.
Sear the seafood: In the same skillet, add 1 tablespoon butter and 1 tablespoon olive oil. When hot, add scallops in a single layer.
Sear 1–2 minutes per side until golden and just opaque. Remove to a plate.
Cook the shrimp: Add the shrimp to the pan and cook 1–2 minutes per side until pink and curled. Remove to the plate with scallops.
Make the Alfredo sauce: Lower heat to medium-low.
Add remaining 1 tablespoon butter and the garlic. Sauté 30 seconds until fragrant. Pour in heavy cream and bring to a gentle simmer.
Finish the sauce: Whisk in parmesan a handful at a time until melted and smooth.
Add nutmeg, lemon juice, and a pinch of pepper. Taste and adjust salt. The sauce should lightly coat a spoon.
Combine: Add zoodles (or shirataki) to the sauce and toss to coat.
Return shrimp and scallops to the pan with any juices. Warm through 1–2 minutes.
Serve: Top with extra parmesan, red pepper flakes if you like heat, and a sprinkle of parsley. Serve immediately.