Heat a stove top grill pan or griddle with cooking spray over medium-high heat. Season calamari with salt and black pepper. Place calamari on hot pan and cook 2 minutes per side stirring with a spoon, until opaque and cooked through. Remove from heat and allow to cool. When calamari is cool enough to handle, cut crosswise into 1/4-inch thick rounds.
Transfer calamari to a medium bowl and add radishes, pimentos and capers.
In a small bowl, whisk together oil, lemon juice and mustard. Using a spoon, stir in dill. Add dressing to calamari mixture and stir to coat. Season, to taste, with salt and freshly ground black pepper.
Arrange lettuce leaves on a serving platter and top with calamari salad.