Technique
Stir the tequila and orange juice with ice first. Pour grenadine slowly down the inside wall of the glass or over the back of a spoon, then leave the drink unstirred so the syrup can settle and feather upward naturally.
A tequila sunrise is a cocktail made of tequila, orange juice, and grenadine syrup, named for its resemblance to a sunrise when made correctly.

TonicDB editorial guide
The Tequila Sunrise gets its name and appearance from density, not from mixing red and orange ingredients together. Tequila and orange juice form the base while grenadine sinks gradually, producing a red-to-gold gradient and a sweeter final portion.
Stir the tequila and orange juice with ice first. Pour grenadine slowly down the inside wall of the glass or over the back of a spoon, then leave the drink unstirred so the syrup can settle and feather upward naturally.
A clear highball shows the gradient best. Garnish with one orange slice and one cherry, and offer a stirrer or straw so the drinker can combine the sweeter lower layer after seeing the sunrise effect.
Pouring grenadine from a height can create a hard red blob rather than a gradual layer, while stirring immediately erases the signature presentation. More grenadine is not better; excess syrup makes the last third cloying.
Fresh orange juice gives a softer, cloudier gradient but a livelier flavor than shelf-stable juice. If the oranges are very sweet, reduce the grenadine slightly rather than adding acid that would move the drink away from its simple three-part character.
These notes explain how to execute and adapt the recipe shown above. Ingredients and serving traditions vary, so taste and adjust thoughtfully.
Contributed by @alfg