How to Make It
Cook bacon in a skillet over medium, stirring often, until crisp, 10 to 12 minutes. Drain on a paper towel–lined plate.
Preheat grill to medium-high (about 450°F). Spray cut sides of cabbage with cooking spray. Grill, uncovered, until charred and tender, 2 to 3 minutes per side. Transfer to a cutting board, and coarsely chop. Transfer to a large bowl. Add bacon, tomatoes, and scallions.
Stir together blue cheese, mayonnaise, oil, vinegar, pepper, and salt in a small bowl. (Mixture will look curdled.) Drizzle over cabbage mixture; toss to coat. Serve immediately.