Purée jalapeño, cilantro, parsley, and 6 tablespoons of the olive oil in a food processor until smooth; season with salt and set aside.

Heat 1 tablespoon of olive in a 15-inch paella pan over medium-high. Add yellow onion and bell pepper and cook, stirring occasionally, until soft, 8–10 minutes. Add garlic and paprikas and stir until fragrant, about 1 minute. Carefully add sherry, bring to a simmer, and cook, stirring constantly, until pan is almost dry, about 3 minutes. Add rice and cook, stirring occasionally, until rice is coated and starting to turn translucent, about 3 minutes. Stir in 6 cups of the broth and saffron and season with salt. Bring broth to a boil, reduce heat, and simmer until rice is cooked. If liquid evaporates and the rice is still al dente, add another cup of water and continue to cook. Nestle clams into the rice and cover, continue to cook until clams begin to open, 12–15 minutes. After 15 minutes, discard any clams that don’t open. Remove from heat (cover) and let rice steam 10 minutes.

While paella cooks, heat a grill pan or skillet over medium-high. Separately, toss green onions and prawns with 1 tablespoon of oil each in respective bowls; season with salt and pepper. Char or grill the green onions, turning occasionally, until greens are charred and bulbs are tender, about 5 minutes. Char or grill prawns until cooked through and shells are charred, about 3 minutes per side. Finally, char or grill lemons until charred, about 1 minute per side.

Tuck the green onions and prawns into the paella. Drizzle dish with the herb infused oil and squeeze lemon juice on top. Place remaining lemons alongside the paella and serve.