1. Heat olive oil in a paella pan over medium heat.
2. Add chopped onion and red bell pepper, cook until soft.
3. Stir in minced garlic and grated tomato, cook for 2 minutes.
4. Add paella rice, stir to coat with the tomato mixture.
5. Pour in chicken broth and saffron with its soaking water, bring to a boil.
6. Reduce heat to low, simmer uncovered for 20 minutes.
7. Add frozen peas, shrimp, and mussels, cook until shrimp are pink and mussels open.
8. Remove from heat, cover with foil, let rest for 5 minutes.
9. Garnish with chopped parsley and lemon wedges before serving.