In a medium saucepan, combine the spelt with enough water to cover by at least 2 inches.
Bring the water to a rolling boil, then reduce the heat to a gentle simmer.
Cover the pot and cook for about 1 hour, or until the spelt is tender but still has a pleasant chew.
Drain the cooked spelt thoroughly in a fine-mesh sieve and transfer it to a large mixing bowl.
Add the chopped red bell pepper, cucumber, shredded carrot, and sliced green onions to the bowl with the spelt and stir to combine.
In a separate small bowl, whisk together the mayonnaise, fresh lemon juice, salt, and cayenne pepper until smooth and creamy.
Pour the dressing over the spelt and vegetable mixture.
Toss gently until everything is evenly coated.
Cover the bowl and chill in the refrigerator for at least 1 hour, or up to 24 hours, to allow the flavors to meld together before serving.
