Heat the paella pan over medium heat and add the olive oil, swirling to coat the surface. Once shimmering, add the chopped onion and minced garlic, cooking until fragrant and translucent, about 5 minutes. You should hear a gentle sizzle and see the onions turn slightly golden.
Add the chopped red bell pepper and cook for another 3 minutes until it softens and releases a sweet aroma. The vegetables should be vibrant and slightly blistered at the edges.
Stir in the chopped zucchini and green beans, cooking for about 4 minutes until they begin to soften and become bright in color. The mixture should smell fresh, with the vegetables maintaining some bite.
Add the rice to the pan, stirring constantly for 2 minutes to toast it slightly. You’ll notice a nutty aroma and the rice grains turning translucent at the edges.
Pour in the saffron-infused broth, ensuring the saffron threads are evenly distributed. Bring the mixture to a gentle simmer, then reduce the heat to low and spread the rice evenly across the pan. Do not stir from now on.
Let the paella cook uncovered for about 15 minutes, gently bubbling. During this time, the rice will absorb the broth, and edges may start to crackle and crisp up a bit, forming the coveted socarrat.
About 5 minutes before finishing, scatter the cherry tomatoes over the top if using, and season with salt and pepper. Continue cooking until the rice is tender and the liquid is mostly absorbed.
Remove the pan from heat, cover it with a clean towel, and let the paella rest for 5 minutes. This allows the flavors to meld and the rice to finish cooking through steam.
Uncover, garnish with lemon wedges, and serve directly from the pan. The rice should be golden, with a slight crispy bottom and fragrant aroma of saffron and roasted vegetables.