Une Bombe Dragonne

Your inner dragon ignites the bombastic fire within your soul! You lob a small grenade of draconic energy at an area within range that you can see. All targets within a 10 foot radius must succeed on a Dexterity saving throw or take 1d4 fire damage.

There are two states in which this spell can be cast. The spellcaster decides which state upon casting. 

In the first state, the grenade detonates on impact. 

In the second state, the spellcaster can delay the detonation until they spend a reaction, anytime before the start of their next turn. 

This spell’s damage increases by 1d4 when you reach 5th level (2d4), 11th level (3d4), and 17th level (4d4).