Remove frozen mixed vegetables from freezer and thaw at room temperature ~30 minutes.
Melt butter or heat oil in saucepan over medium heat.
Add onion and rice and cook 4-5 minutes—until onion is softened, and rice is fragrant and toasted/browned.
Add broth, salt, citrus zest & juice to saucepan and stir to combine. Bring to a boil over medium-high heat.
Once boiling, reduce heat to low and cover pan. Allow to cook for 15 minutes without removing lid.
After 15 minutes, check to ensure rice is tender and liquid is absorbed; if not, cover and cook 2-3 more minutes.
When rice is cooked, stir in thawed frozen veggies.
Remove pan from heat and allow to sit, covered, for another 5-10 minutes.
Serve garnished with fresh parsley and additional citrus juice/zest!