1/4 cup balsamic vinegar
1/4 cup olive oil
2 teaspoons lemon juice
1 teaspoon minced fresh thyme or 1/4 teaspoon dried thyme
1/4 teaspoon salt
1/8 teaspoon coarsely ground pepper
1 beef flat iron steak or top sirloin steak (3/4 pound)
1 package (9 ounces) ready-to-serve salad greens
8 cherry tomatoes, halved
4 radishes, sliced
1/2 medium ripe avocado, peeled and thinly sliced
1/4 cup dried cranberries
Crumbled blue cheese and additional pepper, optional
For dressing, whisk together first six ingredients. Place steak and 1/4 cup dressing in a resealable plastic bag; seal bag and turn to coat. Refrigerate 8 hours or overnight. Reserve remaining dressing; cover and refrigerate until serving.
Drain beef, discarding marinade. Grill steak, covered, over medium heat or broil 4 in. from heat until meat reaches desired doneness (for medium-rare, a thermometer should read 135°; medium, 160°), 6-8 minutes per side. Let stand 5 minutes before slicing.
To serve, divide salad greens among four plates. Top with steak, tomatoes, radishes and avocado; sprinkle with cranberries and, if desired, cheese and pepper. Serve with reserved dressing.