Heat oil in a large nonstick skillet over med-high heat, add onion and saute 5 minutes.
Sprinkle thyme and 1/4 tsp salt over chicken.
Add chicken to pan; saute 6 minutes on each side.
Remove chicken from pan and keep warm.
Reduce heat to medium, add 1/4 tsp salt, preserves, vinegar, and pepper to pan, stirring until preserves melt.
To Serve:.
Spoon sauce over chicken and serve immediately. OR Return chicken to pan and coat chicken evenly, serve immediately.