Combine cabbage, carrots and scallions in a large bowl. Add 2 tablespoons lime juice and ½ teaspoon salt; toss to coat. Combine sour cream, cilantro and the remaining 2 tablespoons lime juice in a small bowl.
Heat a grill pan over high heat. Brush chicken tenders evenly with oil; sprinkle with chili powder and the remaining ½ teaspoon salt. Coat the hot pan with cooking spray. Add the chicken to the pan; cook, turning occasionally, until an instant-read thermometer inserted in the thickest part registers 165 degrees F, 7 to 8 minutes.
Divide the chicken among warm tortillas. Top with the cabbage slaw, the lime crema and jalapeño slices. Garnish with cilantro and serve with lime wedges, if desired.
Note: The jalapeños are hot, but make the dish sing.
