Combine sugar, water, corn syrup, honey, and salt in a medium saucepan over medium heat. Bring to a boil, stirring occasionally to dissolve sugar. Cook, without stirring, until a thermometer registers 240°F, 6 to 8 minutes.
Meanwhile, combine egg whites and cream of tartar in the bowl of a heavy-duty electric mixer fitted with the whisk attachment. Beat on low speed until frothy. When the syrup reaches 235°F, increase mixer speed to medium and continue beating.
Remove sugar mixture from heat. Increase mixer speed to medium-high and slowly pour sugar mixture into egg white mixture down side of bowl. Continue beating until stiff, glossy peaks form and bowl is barely warm to the touch. Use immediately to frost cake. Store any remaining meringue covered at room temperature for 2 days or refrigerate for up to 1 week.