Have all the ingredients at room temperature. Preheat an oven to 200°F. Preheat a Belgian waffle maker.
In a large bowl, whisk the egg yolks. Whisk in the buttermilk, butter and vanilla. Over a sheet of waxed paper, sift together the flour, baking powder, baking soda, salt and sugar. Add the flour mixture to the yolk mixture and whisk until smooth.
In another bowl, whisk the egg whites until stiff peaks form. Using a rubber spatula, fold half of the egg whites into the batter, then fold in the remaining whites. Cook the waffles according to the manufacturer’s instructions. Transfer to a baking sheet and keep warm in the oven.
Preheat a grill pan over medium-high heat. Grill the fruit, turning once, until tender and nicely grill-marked, 4 to 5 minutes total. Transfer to a plate and drizzle with honey.
Place 2 waffle squares on each plate and top with the grilled fruit and yogurt, dividing evenly. Makes eight 4½-inch waffles; serves 4.