Bring a large pot of lightly salted water to a boil over high heat. Add the bow tie pasta and cook until al dente, 8 to 10 minutes. Drain and rinse well with cold water then toss with the olive oil and set aside.
Stir the sour cream, mayonnaise, lemon juice, lemon zest, dill, cayenne pepper and salt until smooth. Fold in the onion, peas, ham, Cheddar cheese and pasta. Garnish with the dill sprigs to serve.