In a bowl, whisk together red pepper, green onions, mayonnaise, yolk, mustard and lemon juice. Stir in crab thoroughly. Season with salt and pepper to taste.
Form rounded tablespoons of crab mixture into slightly flattened 1-in. rounds and gently coat with breadcrumbs, transferring to a shallow tray. Chill crab cakes at least 30 minutes and up to 4 hours.
Preheat oven to 350°F/180°C.
Heat a griddle pan over medium heat and add 1 Tbsp. of olive oil. Working in batches, pan fry the crab cakes until golden brown on both sides, about 2 - 4 minutes per side. Transfer to a baking sheet and place in oven to keep warm while frying remaining cakes, adding more oil as necessary.