Place chicken in small bowl and sprinkle with 1 teaspoon sweet paprika, salt and pepper. Toss to combine well.
Melt 1 tbsp butter in large nonstick skillet over medium-high heat. Add chicken and sauté until just cooked through, about 5 minutes. With slotted spoon, transfer chicken to plate and set aside.
Add remaining ½ tbsp butter to same skillet and sauté onion until softened, about 3 minutes.
Add remaining 2 teaspoons sweet paprika and 1 teaspoon smoked paprika (can use 3 teaspoons sweet paprika, omitting smoked), stir for 10 seconds to combine.
Add chopped tomato and stir to soften a bit, about 1 minute.
Add chicken stock/broth and stir and bring to a boil. Cook at a steady simmer until slightly thickened and sauce thinly coats a spoon, about 6 minutes.
Return chicken and any accumulated juices to pan with sauce mixture, reduce heat to low. Add sour cream and whisk/stir to combine and heat through ~ do not boil. Taste and adjust for salt and pepper. Serve with buttered egg noodles or bread dumplings.