Bring water just below a boil, then remove from heat
Add butterfly pea flowers, lavender buds, juniper berries, cardamom pods, grapefruit peel, rosemary sprigs, and sea salt
Cover and steep 20–30 minutes
Strain through a fine sieve or coffee filter until clear with no particulates
Pour into an airtight glass bottle and refrigerate once no longer hot
Fill a champagne flute or highball glass with ice
Pour blue brew to halfway mark
Top with tonic water and watch the color drift to violet
Garnish with rosemary and/or a thin lemon slice
