Using an electric mixer or stand mixer fitted with whisk attachment, whisk together sugar, oil and lemon zest until combined. Add one egg at a time, beating well after each. Whisk in buttermilk, lemon juice, and lemon extract. Add flour mixture all at once and whisk until smooth, about 1 minute. Carefully add boiling water with mixer on low and whisk until incorporated and batter is smooth, increasing speed when water has been incorporated, about 1 minute.