Preheat the oven to 400°F. Peel and thinly slice the onion. Peel and thinly slice 4 cloves garlic. Trim and chop the green beans into 2 inch pieces.
Place a paella pan or large ovenproof skillet over medium-high heat with 1 tbsp olive oil. Add the onion, and garlic, sprinkle with salt, and cook, stirring occasionally, until the vegetables soften, about 3 to 5 minutes. Add the short grain white rice and cook, stirring occasionally, until it’s glossy, about 1 to 2 minutes.
Add the paella seasoning to the skillet and cook, stirring frequently, until the spices are fragrant, about 1 minute. Add 2 cups water and ½ tsp salt, and bring the rice to a boil. Reduce heat to low and let rice simmer while you prepare the next batch of vegetables, about 5 to 7 minutes.
In a large bowl, toss the green beans, fava beans, and roasted red peppers with 1 tbsp olive oil and a pinch of salt and pepper. Add the vegetables on top of the rice, distributing evenly, and place the skillet into the oven. Bake until the rice is cooked, about 12 to 15 minutes.
Place a small skillet over medium heat and add the almonds. Toast until fragrant and lightly browned, about 2 to 3 minutes. Roughly chop the toasted almonds.
Once the rice is finished, return the skillet to medium heat on the stovetop and cook until the bottom of the rice becomes crisp, at least 2 to 3 minutes. Once the rice is crispy, top the dish with the juice from half the lemon. Cut remaining the lemon half into wedges. Sprinkle the Paella Valencia with toasted almonds and serve with lemon wedges.