Heath the vegetable broth.
If using saffron threads, soak the saffron in a small bowl with 4 tablespoons of broth and let it sit for 10 minutes to steep.
Add some olive oil to a large skillet on medium heat. Add the onion and garlic and sauté until the onion is translucent.
At this point, add bell peppers, carrots, and sauté for 3 to 5 minutes—season with a bit of salt. Then add the frozen peas, olives, spinach, and finally rice. Mix and stir well, cook the rice for a couple of minutes, then add the saffron.
Pour 3 1/2 cups of hot broth slowly in the pan, making sure it's evenly distributed. Bring to the boil and then reduce the heat to medium and let it cook uncovered. Top with the artichokes. Never stir the rice.
Let the vegetable paella cook for 15-18 minutes. After 10 minutes, check the rice. If needed, add more broth, 1/3 cup at a time. Increase the heat during the last couple of minutes to create a crispy bottom.
Remove the pan from the heat, top with some cherry tomatoes, and cover it with a lid or tin foil and let the paella rest for 5-10 minutes (note 7).
Garnish with the fresh chopped parsley and lemon wedges before serving.