Start by bringing a large pot of salted water to a boil and cook the spaghetti until just al dente, about 8-10 minutes. Drain and set aside, reserving a cup of pasta water.
While the pasta cooks, drain the soaked cashews and add them to your blender along with nutritional yeast, smoked paprika, plant-based milk, lemon zest, and lemon juice. Blend until smooth and creamy, scraping down the sides as needed.
Heat olive oil in a skillet over medium heat, about 160°C (320°F). Add the finely chopped onion and minced garlic, sautéing until fragrant and translucent, about 2 minutes.
Add the vegan bacon strips to the skillet and cook until crispy and smoky, about 3-4 minutes. Remove from heat and set aside.
Pour the blended cashew sauce into the skillet with the sautéed onion, garlic, and vegan bacon. Warm gently over low heat, stirring continuously, until the sauce is heated through and slightly thickened, about 2-3 minutes. Add reserved pasta water a tablespoon at a time if the sauce needs loosening.
Add the cooked spaghetti to the skillet and toss everything together until the pasta is evenly coated with the sauce. Let it cook for another minute to meld the flavors, then taste and adjust seasonings with salt, pepper, or more lemon if desired.
Serve immediately, garnished with additional lemon zest or fresh herbs if you like, and enjoy the creamy, smoky vegan carbonara.
