Heat grill to medium high (350-400 degrees).
Steam cauliflower florets for 4 minutes and then place in an ice bath or run under cold water to stop them from cooking further.
In large bowl whisk together soy sauce, olive oil, and lemon juice. Toss with cauliflower and then season with salt and pepper.
Place cauliflower over the direct heat and close the grill. Grill for 5 minutes, then turn and rotate. Rotate cauliflower so all sides get grill marks or some char.
Remove and serve warm with pesto drizzle on top and as dipping sauce.