Pavlova with Rhubarb and Pistachios

Ingredients

• 1 3/4 cups, sugar – divided
• 1 tablespoon, cornstarch
• 4 large, egg whites – room temperature
• 1 tablespoon, fresh lemon juice – from one lemon
• 1 teaspoon, fresh lemon juice
• Coarse salt
• 1 pound, rhubarb – trimmed and sliced on the bias into 2-inch pieces
• 1/4 cup, water
• 1 1/2 cups, heavy cream
• 1 teaspoon, vanilla extract
• Chopped roasted unsalted pistachios – for garnish