Cook pasta according to package directions. Drain and set aside.
In a medium saucepan over medium heat, add butter. When melted, add flour. Whisk until browned and slightly bubbly, about 7 minutes. Add salt, pepper, and garlic powder; whisk to combine.
While whisking, slowly pour in milk. Continue to whisk until mixture thickens, about 5-7 minutes. Add Daiya shreds; whisk until melted, about 3 minutes.
Add pasta to cheese mixture; stir to evenly coat the pasta in the cheese sauce. Add a bit more milk if you want the sauce to be thinner.