Mix the vinaigrette ingredients in a larger bowl, season with salt and leave at the bottom. Place spinach and mint leaves on top.
Score the chicken breast in 2 places (as shown in the photo), place on a heated grill (or grill pan) with onion and lemon, salt it.
Cover the chicken with pineapple slices sprinkled with pepper and a bit of sugar and grill on one side for 8 minutes, then flip to the other side and grill for another 5 minutes (remove the pineapple from the chicken at this point and grill it to the side).
Remove from the pan, after waiting 3 minutes slice the meat into strips, add to the salad together with sliced pineapple and finely chopped onion, mix just before serving.