Begin by spiralizing the zucchini into zoodles using a spiralizer. If you don't have a spiralizer, you can use a vegetable peeler to create thin strips resembling noodles. Set the zoodles aside for later use.
In a large skillet, heat the olive oil over medium heat. Once the oil is shimmering, add the minced garlic and sauté for 1-2 minutes, stirring frequently, until the garlic becomes fragrant but takes care not to let it brown.
Next, add the steamed cauliflower florets to the skillet and pour in the vegetable broth. Bring the mixture to a gentle simmer, allowing it to cook for approximately 5 minutes until the cauliflower is heated through.
Remove the skillet from the heat. Using an immersion blender, blend the cauliflower and broth mixture until it is smooth and creamy. If you don't have an immersion blender, carefully transfer the mixture to a regular blender and blend until smooth, then return it to the skillet.
Stir in the nutritional yeast, freshly squeezed lemon juice, and lemon zest into the creamy cauliflower mixture. Mix well to combine and season with salt and freshly cracked pepper to taste.
Using the same skillet that you used for the garlic, add the zoodles and toss them gently in the residual heat for about 2-3 minutes, or until they are just tender but still have a bit of bite.
Pour the lemon garlic Alfredo sauce over the zoodles, gently tossing until all the noodles are well coated with the sauce and heated through, about 1-2 minutes.
Serve immediately, garnished generously with freshly chopped parsley on top to add a pop of color and freshness.
Notes
For a richer flavor, consider adding more nutritional yeast or a pinch of red pepper flakes for heat.