Boil the pasta in salted water per the directions on the package until al dente. Drain well.
Stir the frozen peas into the hot pasta.
Dice the ham, cheese, red onion, yellow pepper, green onions and tomatoes.
Set the tomatoes and cheese cubes aside.
In a large mixing bowl, whisk together the dressing ingredients. Season with salt and black pepper to your taste, then add the chopped ham and veggies reserving a few green onion tops for garnishing.
Do not add the tomatoes or cheese at this point. Mix well.
Pour the pasta and peas into the mixing bowl with the dressing. Stir until fully combined.
Place into the refrigerator to allow the pasta to cool for around 15 minutes.
Add the chopped tomatoes and cubed cheese.
Taste and adjust the seasonings if needed.
Chill for at least 3 hours before serving.
I recommend waiting until the pasta has cooled to add the chopped tomatoes and cheese cubes. This will prevent the tomatoes from watering down the dressing and it won't affect the texture of the cheese.