Make the steak: Preheat a grill or grill pan to medium. Mix the chili powder, brown sugar, cumin and smoked paprika in a small bowl. Season the steaks with salt and pepper and rub with the spice mixture; set aside.
Make the vinaigrette: Puree the cherry tomatoes, lime juice, adobo sauce and honey in a blender until smooth. With the machine running, add the olive oil and puree until smooth. Season with salt and pepper.
Brush the steaks with olive oil and grill 4 to 5 minutes per side for medium rare. Transfer to a cutting board and let rest 10 minutes. Meanwhile, brush the red onion slices with olive oil; season with salt and pepper. Grill the onion, turning occasionally, until softened and charred in spots, about 8 minutes. Thinly slice the steak against the grain. Roughly chop the onion.
Assemble the salad: Divide the lettuce among plates. Top with the onion, steak, avocado, heirloom tomatoes, jicama and queso fresco. Drizzle with about half of the vinaigrette and sprinkle with the cilantro. Serve with the remaining vinaigrette.