Preheat the oven to 400°F. Peel and thinly slice the onion. Peel and thinly slice the garlic. Trim and chop the green beans into 2 inch pieces. Trim the ends off of the delicata squash and use a spoon to scoop out the seeds. Cut the squash into thin, ¼ inch thick rounds.
Place a paella pan or large ovenproof skillet over medium-high heat with 1 tbsp olive oil. Add the sliced onion and sliced garlic, sprinkle with salt, and cook, stirring occasionally, until the vegetables soften, about 3 to 5 minutes. Add the short-grain 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 until it begins to cook, about 4 to 5 minutes.
Drain and rinse the butter beans and pat dry with paper towels. In a large bowl, toss the chopped green beans, squash rounds, butter beans, 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.
Trim, deseed, and mince the red Fresno pepper. Mince the capers. Mince the olives, discarding any pits. Add the minced pepper, capers, olives, juice from just half the lemon, and 1 tbsp olive oil to a medium bowl and mix the caper drizzle well to combine.
Once the rice is finished, return the skillet to medium heat on the stovetop and cook until the bottom of the rice becomes crisp, about 2 to 3 minutes. Cut remaining lemon half into wedges. Drizzle the paella with caper drizzle, top with almonds, and serve with lemon wedges.