Bring a large pot of salted water to a boil.
Whisk the mayonnaise, sour cream, lemon juice, 1/2 teaspoon salt and a few grinds of pepper together in a large bowl.
Add the pasta to the boiling water and cook according to the package directions. Drain and rinse under cold water to cool. Add to the bowl with the dressing.
Add the spinach, basil, and scallions, Gouda and tomato to the bowl and toss to combine. Season with salt and pepper. The pasta salad is best if served right away.
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