For the artichokes: Fill a large pot with cold water. Squeeze the lemons into the water, and then drop them into the pot. Add the olive oil and salt. Add the artichokes and cook until a paring knife inserted into the center meets with a little resistance, about 15 minutes. Drain and shock in cold water for 30 seconds. Drain again and transfer to a sheet lined with paper towels to dry.
While the artichokes are cooking, make the vinaigrette: Whisk the mustard, honey, lemon zest and juice and some salt and pepper in a medium bowl. Slowly whisk in the olive oil until emulsified.
Heat a charcoal or gas grill to high. Halve the artichokes, brush with canola oil and season with salt and pepper. Grill until golden brown and slightly charred on both sides, about 2 minutes per side. Transfer to a large bowl and toss with the vinaigrette, herbs and red pepper flakes.