1. Cut pineapple into rings about half-inch thick, removing tough core and rind. Heat grill or grill pan over medium-high heat until very hot. Place pineapple rings and jalapeño halves cut-side down on hot grill.

2. Grill pineapple and jalapeño for 4-5 minutes per side until you see char marks and pineapple caramelizes. Jalapeño should be slightly charred and softened. Remove from grill and let cool completely for at least 30 minutes before blending.

3. Cut cooled grilled pineapple into chunks. Measure 1 cup of grilled pineapple chunks and add to blender along with grilled jalapeño and 1 cup water. Blend on high speed until completely smooth, about 30-45 seconds.

4. Set fine mesh strainer over a large bowl. Pour blended mixture through strainer, using spoon to press down and extract all liquid. Leave fibrous bits and strings behind. You need about 1.5 cups of smooth grilled pineapple juice.

5. In cocktail shaker, combine tequila, lime juice, orange liqueur, agave nectar, and half a cup of grilled pineapple mixture. Add generous handful of ice and shake vigorously for 20 seconds until ice cold. Taste and adjust sweetness if needed.

6. Run lime wedge around rim of glasses and dip in salt or Tajín. Fill glasses with fresh ice. Strain margarita mixture into glasses, dividing evenly. Garnish with grilled pineapple slice and jalapeño slice if desired. Serve immediately.