• About 1 tsp. lemon juice, or more if needed
Rinse clams in several changes of cold water. Scrub with a stiff brush. Discard any that are open.
Pour wine into a heavy pan large enough to hold the clams. Bring to a boil and then reduce by half. Add clams, cover and cook over high heat for 2 to 3 minutes until clams open. Remove from heat; discard any clams that are not open. Strain the cooking liquid (reserving liquid) through a chinois or a strainer lined with a coffee filter. Set liquid aside in separate bowl.
In a large, wide skillet, heat olive oil over medium heat. Add onion or shallots, sauté until tender, about 2 to 3 minutes. Add garlic and red pepper, and cook until fragrant, about 1 minute. Add tomatoes and juice, oregano, orange zest and liquid from the clams. Add salt and pepper, bring to simmer and cook for 25 minutes, stirring frequently.
Stir clams into the tomato sauce and heat through. Serve in wide soup bowls. Sprinkle with parsley. Drizzle with olive oil and a few drops of lemon juice.