Peel, core, and slice the pineapple into evenly sized ¾-inch thick rings for even grilling.
In a small bowl, combine the dark brown sugar, maple syrup, cinnamon, and vanilla extract. Stir until a smooth, thick glaze forms.
Let the glaze rest for about 1 minute so the cinnamon fully blends with the other ingredients.
Preheat your grill to 350°F (175°C) or medium heat.
Brush both sides of each pineapple ring generously with the brown sugar glaze.
Place the coated pineapple rings directly on the hot grill grates.
Grill for 4 to 8 minutes per side, depending on your grill's heat, until the pineapple develops beautiful grill marks and the glaze caramelizes.
Rotate the pineapple halfway through cooking on each side for attractive crosshatch grill marks.
Remove the grilled pineapple from the grill and transfer it to a serving platter.
Finish with a light sprinkle of coarse sea salt to enhance the sweetness and add a subtle crunch.
Serve immediately while warm.